Twins

Kiddushin 12b ~ The Surprising Birth of Rebbi Chiyyah's Twins

Today’s page of Talmud continues an analysis of the fluctuating value of a perutah, the minimum amount that a man must pay to purchase his wife. For reasons that need not detain us, Rav Chisdah mentions a strange fact about Yehudit, the wife of the Rebbi Chiyyah:

קידושין יב, ב

לָאו הַיְינוּ דִּיהוּדִית דְּבֵיתְהוּ דְּרַבִּי חִיָּיא, דַּהֲוָה לַהּ צַעַר לֵידָה

Rav Chisdah explained: Is this not similar to the case of Yehudit, wife of Rabbi Chiyyah, who would have painful childbirths [and therefore wished to leave Rabbi Chiyyah]?

Elsewhere in the Talmud, (on a page that we will study on April 22nd, 2027,) there is more detail about one of Yehudit’s pregnancies. When I first read the story, I considered it to be entirely fanciful. It was impossible, so it seemed to me, to have actually occurred. Then I read the science, and I changed my mind. Let’s see if it changes yours. So let’s take a look at Niddah 27a:

Yehudit’s Special Twins

נדה כז, א

א"ר אבין בר רב אדא אמר רב מנחם איש כפר שערים ואמרי לה בית שערים מעשה ונשתהה ולד אחד אחר חבירו ג' חדשים והרי הם יושבים לפנינו בבית המדרש ומאן נינהו יהודה וחזקיה בני רבי חייא

Twins image.jpg

Rabbi Avin bar Rav Adda says that Rav Menachem of the village of She’arim, and some say that he was from Beit She’arim, says: An incident occurred where one offspring remained in the womb after the other was born for three months, and both twins are sitting before us in the study hall. And who are they? They are Yehuda and Chizkiyya, the sons of Rabbi Chiyyah.

Delayed Interval births - what you need to know

When you look at the medical literature, it turns out that there are many case reports of delayed-interval twin births. This is probably because the number of multiple pregnancies has increased due to the expansion of assisted reproductive technology. In nearly all, the first twin died soon after delivery because it is too premature to survive.

Here is just one example. In 2019 a group from the Department of Clinical and Experimental Medicine at the University of Pisa in Italy published a case report with a very lengthy title: Delayed delivery of the second twin: Case report and literature review of diamniotic dichorionic twin pregnancy with very early preterm premature rupture of membranes. A mother went into very early labor and delivered the first of two twins at about 26 weeks’ gestation. The second twin remained in her uterus, and was delivered 29 days later by cesarean section. The first very premature twin died, but happily the second survived and at 6-month follow-up, “no neurological, cardiac or other defects could be detected.”

A 2016 systematic review found 13 articles reporting a total of 128 cases of delayed-interval twin births. It reported that the second born twin had a significantly lower mortality risk compared to the first born (relative risk = 0.44, 95% confidence interval = 0.34 – 0.57, P<0.0001,) which makes sense since the second twin had the benefit of a longer period of uterine gestation.

Results of individual studies, mortality of the second born versus the first born. From Feys S. Jacquemyn Y. Delayed-interval delivery can save the second twin: evidence from a systematic review. Facts Views Vis Obgyn, 2016, 8 (4): 223-231.

Results of individual studies, mortality of the second born versus the first born. From Feys S. Jacquemyn Y. Delayed-interval delivery can save the second twin: evidence from a systematic review. Facts Views Vis Obgyn, 2016, 8 (4): 223-231.

Interval twin births - the world Record

There is even an official world record for delayed-interval twin births. According to Guinness World Records, the longest verified interval between the birth of twins is 87 days (and 1 hour 45 minutes). Twin girls Amy Ann and Kate Marie Elliot were born 87 days apart, at Waterford Regional Hospital in County Kilkenny, Ireland. Amy was born prematurely on 1 June 2012 and Kate followed on 27 August. Because Amy Ann was born at 09:16 and Kate Marie at 11:01, the exact interval is 87 days, 1 hour and 45 minutes. That’s a little shy of three months. Just like the story in the Talmud.

Actually, there is a report that in 2018 this record was beaten, though I’d be careful about believing what you read in perhaps the smuttiest paper in Britain, The Sun. But here it is anyway. And note that the twins were born just over three months apart.

Mum Oxana went into labour initially at just 26 weeks pregnant and gave birth to Liana prematurely on November 17, 2018. She weighed just 2lbs. Three months later, she finally gave birth to Leonie - four days after her initial due date. A spokeswoman for Holweide hospital in Cologne said: "After the birth of the first twin, the cervix closed again and the unborn sister could remain in the womb.” As contractions ceased, doctors decided that Oxana could carry her second baby girl to term.

Maternity chief Dr Uwe Schellenberger said: "The conditions were very good as well due to the existing second placenta and we wanted to try to let the second child mature as long as possible in the womb." Leonie was born a total of 97 days difference with her twin sister Liana and was born weighing 8.1lbs. Dr Schellenberger said: "It's also a rare case for our maternity clinic, but it was not the first time that twins were born on different days at the Holweide hospital. "But the time difference of 97 days is unique for us and also special worldwide."

According to the hospital, the girls may have broken a world record. "Such a 'two-time twin birth' is very rare worldwide," the spokeswoman explained. "According to our own research, twins with a time difference of 87 days were born in Ireland in 2012." Liana spent her first few weeks in a neonatal care unit at the hospital where she stayed until she was strong enough to go home.Both girls now weigh around 12.5lbs and have developed well.The spokeswoman said that they've both been reunited at their family home and are set to grow up healthy.

What would it have taken for Yehuda and Chizkiyya to survive?

In its English translation, the Artscroll Talmud introduces this story in Niddah as a “fantastic incident.” If by “fantastic” it means “based on fantasy” or “not real,” it this commentary is mistaken. If however, it means “so extreme as to challenge belief,” well, then it is correct. It is indeed an extremely unlikely story, but not an impossible one. Here is what it would take for the story of Yehudit and her twins to have actually occurred.

  1. The first born twin would have had to be born at around six months gestation. Even today, with neonatal intensive care units, incubators, respirators, antibiotics and specialist staff, this is the very limit of survivability. The mortality rate in babies born between the 23rd and 25th week is 32%.

2. Next, Yehudit, the mother, would have had to survive the preterm premature rupture of the amniotic membranes which carries a risk of 17-52% of introducing an intrauterine infection, and a risk of 4-22% of causing maternal sepsis.

3.Then Yehudit would have had to carry the second twin to a full-term birth, and that twin must survive.

4. Finally - and this is important - the Talmud lets us know that the boys were “sitting in the study hall.” In other words, they both had a fairly normal cognitive ability, which in very premature infants is often not the case.

Tosafot Agrees - it is really rare

The chances of all this happening are very low. In fact the medieval compendium of commentaries on the Talmud known as Tosafot makes this very point (Niddah 26b ד’ה ילדה):

ילדה ואח"כ הפילה שליא אפי' עד י' ימים אין חוששין לולד אחר. אע"ג דאמר לקמן דנשתהא הולד שלשה חדשים מ"מ לא שכיח וכל כמה דלא חזינן לא חיישינן

Even though the Talmud states that “one offspring remained in the womb after the other was born for three months,” this is not common. And when something is so rare that it almost never happens, it may [for practical purposes] be ignored.

But a very low likelihood of something happening does not make it impossible. The three month delay in the birth of the boys was indeed scientifically possible. I hope Yehuda and Chizzkiya realized just how lucky they were.

“We feel so blessed to be here,” their mother said. “The only thing that’s gotten me through this... is to say, ‘God is in control,’” she noted.
— Kristen Miiler, mother of twins born five and a half weeks apart. See "Doctors stunned by rare twins born more than five weeks apart." Washington Post April 7, 2016




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Yevamot 98b ~ On the Formation of Twins

Buried in a discussion of paternity, Rava states that the mechanism of the development of twin brothers is as follows:  "דטפה אחת היה ונחלקה לשתים"  - "there was one drop of semen that split into two".

Aristotle (384-322 BC) believed that twins were caused by too much seed (which does make a certain intuitive sense I suppose). In the thirteenth century the German theologian Albertus Magnus updated this theory, and suggested that twins were generated when the woman experienced too much sexual pleasure during intercourse. This redistributed the seed throughout the uterus, resulting in twins. 

We now know that there are actually only two ways that twins are formed, and neither depends on sperm splitting, too much seed, or an abundance of sexual pleasure. In monozygotic or identical twins (though they are not always literally identical), one sperm fertilizes one egg, and the resulting zygote then divides into two. Since the two offspring zygotes originated from the same "mother" zygote, they are genetically identical - and hence the twins (or triplets, if the zygote splits three ways) are identical and of course of the same sex.

Formation of identical (monozygotic) twins. Courtesy Womenshealth.gov

In dizygotic or fraternal twins, two sperm fertilize two eggs and the two resulting zygotes grow together in the same womb at the same time. They are not genetically identical, and are really two siblings who just happen to be sharing a womb at the same time. 

Formation of fraternal (dizygotic) twins. Courtesy Womenshealth.gov

That's it. No sperm splits.  Sorry.

Fun facts about twins, Israeli and others

  • For reasons that are not clear, the rate of dizygotic twins varies across the world, (highest in sub-Saharan Africa, lowest in Asia) and varies across women by body habitus (taller women are more likely to have twins - who knew?) and age (older women are four times more likely to have twins) and varies across time (possibly highest when conception is in the summer and fall).

Twinning Rates in the USA, Europe, Australia and Asia. From Hoekstra et al. Dizygotic Twinning. Human Reproduction Update 2007.14; 37-47.

  • From 1915, when records were first started, through the 1970s, the rate of twin births in the US was a constant 2% of all births. But in the early 1980s the number of twin births in the US more than doubled, and today that rate is over 3%. The cause, as you may have guessed, is the increased use of reproductive technologies.

One in every 30 infants born in 2009 was a twin
— US Dept of Health and Human Services. NCHS Data Brief Jan 2012
  • The states that saw the greatest increase in twin birth rates were Connecticut, Hawaii, Massachusetts, New Jersey and Rhode Island. In these states, the twin birth rate more than doubled!

Percentage Increase in Twin Birth Rates 1980-2009. From NCHS Data Brief #80. Jan 2012.

  • Finally, although the rate of twin births has increased for women of all ages over the last three decades, in women older than 40 the rate of twin births increased by 200%. There are at least two causes for this dramatic rise. First, as more women postpone childbirth, more are having children later in life, and older women, as we have already seen, are more likely to have (dizygotic) twins. And secondly, more older women are using assisted reproduction techniques, which also increases the rate of twin conceptions.

  • In Israel, the incidence of twin births increased three fold in the three decades before 2001, a rate even higher than the increase in the US. The authors of a 2004 study on multiple births in Israel concluded that the "increased incidence of multiple births is explained by the special significance attributed to motherhood in Israeli society, which is met by the socio-political milieu and the availability of assisted reproductive technologies". Indeed.

  • The incidence of twin births in higher in Jewish than it is in Arab Israelis.  This is likely explained by their greater use of assisted reproductive technologies (like in-vitro fertilization).  

Incidence of twin births in Jewish and Arab populations of Israel, 1994-2001. From Blickstein I, Baor L. Trends in multiple births in Israel. Harefuah 2004; 143 (11): 794-798.


The Talmud wasn't exactly accurate about how twins are formed, but elsewhere it does capture the sense of wonder that so many of us feel as we hold a newborn baby (or two). It's a transcendent moment in which we may, for a fleeting moment, feel the divine.   

תנו רבנן שלשה שותפין יש באדם הקב”ה ואביו ואמו. אביו מזריע הלובן...אמו מזרעת אודם ... והקב”ה נותן בו רוח ונשמה וקלסתר פנים...

Our Rabbis taught: There are three partners in the creation of a person, the Holy One, blessed be He, the father and the mother. The father supplies the white...the mother supplies the red...and the Holy One, blessed be He, supplies the spirit and the breath and the beauty...
— Niddah, 31a

  

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Niddah 27a ~ Delayed Interval Twin Births and the Unlikely (But Plausible) Survival of Yehuda and Chizkiyya

Today the Talmud recounts the survival of twin boys, Yehuda and Chizkiyya. When I first read the story, I considered it to be entirely fanciful. It was impossible, so it seemed to me, to have actually occurred. Then I read the science, and I changed my mind. Let’s see if it changes yours.

נדה כז, א

א"ר אבין בר רב אדא אמר רב מנחם איש כפר שערים ואמרי לה בית שערים מעשה ונשתהה ולד אחד אחר חבירו ג' חדשים והרי הם יושבים לפנינו בבית המדרש ומאן נינהו יהודה וחזקיה בני רבי חייא

Twins image.jpg

Rabbi Avin bar Rav Adda says that Rav Menachem of the village of She’arim, and some say that he was from Beit She’arim, says: An incident occurred where one offspring remained in the womb after the other was born for three months, and both twins are sitting before us in the study hall. And who are they? They are Yehuda and Chizkiyya, the sons of Rabbi Chiyya.

Delayed Interval births - what you need to know

When you look at the medical literature, it turns out that there are many case reports of delayed-interval twin births. This is probably because the number of multiple pregnancies has increased due to the expansion of assisted reproductive technology. In nearly all, the first twin died soon after delivery because it is too premature to survive.

Here is just one example. Last year a group from the Department of Clinical and Experimental Medicine at the University of Pisa in Italy published a case report with a very lengthy title: Delayed delivery of the second twin: Case report and literature review of diamniotic dichorionic twin pregnancy with very early preterm premature rupture of membranes. A mother went into very early labor and delivered the first of two twins at about 26 weeks’ gestation. The second twin remained in her uterus, and was delivered 29 days later by cesarean section. The first very premature twin died, but happily the second survived and at 6-month follow-up, “no neurological, cardiac or other defects could be detected.”

A 2016 systematic review found 13 articles reporting a total of 128 cases of delayed-interval twin births. It reported that the second born twin had a significantly lower mortality risk compared to the first born (relative risk = 0.44, 95% confidence interval = 0.34 – 0.57, P<0.0001,) which makes sense since the second twin had the benefit of a longer period of uterine gestation.

Results of individual studies, mortality of the second born versus the first born. From Feys S. Jacquemyn Y. Delayed-interval delivery can save the second twin: evidence from a systematic review. Facts Views Vis Obgyn, 2016, 8 (4): 223-231.

Results of individual studies, mortality of the second born versus the first born. From Feys S. Jacquemyn Y. Delayed-interval delivery can save the second twin: evidence from a systematic review. Facts Views Vis Obgyn, 2016, 8 (4): 223-231.

Interval twin births - the world Record

There is even an official world record for delayed-interval twin births. According to Guinness World Records, the longest verified interval between the birth of twins is 87 days (and 1 hour 45 minutes). Twin girls Amy Ann and Kate Marie Elliot were born 87 days apart, at Waterford Regional Hospital in County Kilkenny, Ireland. Amy was born prematurely on 1 June 2012 and Kate followed on 27 August. Because Amy Ann was born at 09:16 and Kate Marie at 11:01, the exact interval is 87 days, 1 hour and 45 minutes. That’s just shy of three months. Just like the story in the Talmud.

Actually, there is a report that in 2018 this record was beaten, though I’d be careful about believing what you read in perhaps the smuttiest paper in Britain, The Sun. But here it is anyway. And note that the twins were born just over three months apart.

Mum Oxana went into labour initially at just 26 weeks pregnant and gave birth to Liana prematurely on November 17, 2018. She weighed just 2lbs. Three months later, she finally gave birth to Leonie - four days after her initial due date. A spokeswoman for Holweide hospital in Cologne said: "After the birth of the first twin, the cervix closed again and the unborn sister could remain in the womb.” As contractions ceased, doctors decided that Oxana could carry her second baby girl to term.

Maternity chief Dr Uwe Schellenberger said: "The conditions were very good as well due to the existing second placenta and we wanted to try to let the second child mature as long as possible in the womb." Leonie was born a total of 97 days difference with her twin sister Liana and was born weighing 8.1lbs. Dr Schellenberger said: "It's also a rare case for our maternity clinic, but it was not the first time that twins were born on different days at the Holweide hospital. "But the time difference of 97 days is unique for us and also special worldwide."

According to the hospital, the girls may have broken a world record. "Such a 'two-time twin birth' is very rare worldwide," the spokeswoman explained. "According to our own research, twins with a time difference of 87 days were born in Ireland in 2012." Liana spent her first few weeks in a neonatal care unit at the hospital where she stayed until she was strong enough to go home.Both girls now weigh around 12.5lbs and have developed well.The spokeswoman said that they've both been reunited at their family home and are set to grow up healthy.

What would it have taken for Yehuda and Chizkiyya to survive?

In its English translation, the Artscroll Talmud introduces this story calling it a “fantastic incident.” If by “fantastic” it means “based on fantasy” or “not real,” it is mistaken. If however, it means “so extreme as to challenge belief” well then it is correct. It is indeed an extremely unlikely story, but not an impossible one. Here is what it would take to have actually occurred.

  1. The first born twin would have had to be born at around six months gestation. Even today, with neonatal intensive care units, incubators, respirators, antibiotics and specialist staff, this is the very limit of survivability. The mortality rate in babies born between the 23rd and 25th week is 32%.

2. Next, the mother would have had to survive the preterm premature rupture of the amniotic membranes which carries a risk of 17-52% of introducing an intrauterine infection, and a risk of 4-22% of causing maternal sepsis.

3.Then the mother would have had to carry the second twin to a full-term birth, and that twin must survive.

4. Finally - and this is important - the Talmud lets us know that the boys were “sitting in the study hall.” In other words, they both had a fairly normal cognitive ability, which in very premature infants is often not the case.

Tosafot Agrees - it is really rare

The chances of all this happening are very low. In fact the medieval compendium of commentaries on the Talmud known as Tosafot makes this very point (Niddah 26b ד’ה ילדה):

ילדה ואח"כ הפילה שליא אפי' עד י' ימים אין חוששין לולד אחר. אע"ג דאמר לקמן דנשתהא הולד שלשה חדשים מ"מ לא שכיח וכל כמה דלא חזינן לא חיישינן

Even though the Talmud states that “one offspring remained in the womb after the other was born for three months,” this is not common. And when something is so rare that it almost never happens, it may [for practical purposes] be ignored.

But a very low likelihood of something happening does not make it impossible. The three month delay in the birth of the boys was indeed scientifically possible. I hope Yehuda and Chizzkiya realized just how lucky they were.

“We feel so blessed to be here,” their mother said. “The only thing that’s gotten me through this... is to say, ‘God is in control,’” she noted.
— Kristen Miiler, mother of twins born five and a half weeks apart. See "Doctors stunned by rare twins born more than five weeks apart." Washington Post April 7, 2016




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Mencahot 37a ~ Conjoined Twins

מנחות לז, א

בעא מיניה פלימו מרבי מי שיש לו שני ראשים באיזה מהן מניח תפילין א"ל או קום גלי או קבל עלך שמתא אדהכי אתא ההוא גברא א"ל איתיליד לי ינוקא דאית ליה תרי רישי כמה בעינן למיתב לכהן אתא ההוא סבא תנא ליה חייב ליתן לו י' סלעים

The Sage Peleimu asked Rabbi Yehuda HaNasi: In the case of one who has two heads, on which of them does he don tefillin [phylacteries]? Rabbi Yehuda HaNasi said to him: Either get up and exile yourself from here or accept upon yourself excommunication [for asking such a ridiculous question]. In the meantime, a certain man arrived and said to Rabbi Yehuda HaNasi: A firstborn child has been born to me who has two heads. How much money must I give to the priest for the redemption of the firstborn? A certain elder came and taught him: You are obligated to give him ten sela,the requisite five for each head.

Conjoined parapagus twins. This is likely the case brought before Rebbi Yehuda HaNasi, because these twins may have two, three, or four arms and two or three legs. The twins share the umbilicus, lower abdomen, pelvis and genitourinary tract. From Pi…

Conjoined parapagus twins. This is likely the case brought before Rebbi Yehuda HaNasi, because these twins may have two, three, or four arms and two or three legs. The twins share the umbilicus, lower abdomen, pelvis and genitourinary tract. From Pierro A. Kiley E. Spitz, L. Classification and clinical evaluation. Seminars in Pediatric Surgery 24 (2015): 207–211.

The epidemiology and classification of Conjoined Twins


Rabbi Yehuda HaNasi was indignant: there surely could be no such creature as a human with two heads. His belief was quickly challenged when he was asked about a real case of a child born with two heads - what today we call conjoined twins.

Today, conjoined twins are rare. According to a recent paper in Seminars in Pediatric Surgery, the incidence of conjoined twins ranges from 1:50,000 to 1:100,000 live births, although it is higher in Africa and in South-East Asia. Most pregnancies that are carrying conjoined twins result in miscarriages and stillbirths. Despite this, 18% of all conjoined infants survive to delivery: however about a third die in the first 24 hours, and only 18% of all conjoined twins survive longer than that. If these survival rates were similar in the times of the Mishnah (and back then the survival rate was surely even lower,) the reaction of Rabbi Yehuda’ HaNasi to the question was certainly understandable. It was extremely unlikely that they would live long enough to start the mitzvah of tefillin.

Parapagus twins lie side to side with ventrolateral fusion. The twins share the umbilicus, lower abdomen, pelvis (single symphysis pubis), and genitourinary tract. They can have anorectal anomaly and colovesical fistula and may be at risk of anencephaly. The conjoined pelvis usually has a single symphysis pubis and one or two sacra. The thorax may be involved. The twins can have (i) separate heads (dicephalic) but the entire trunk is conjoined and (ii) separate thoraces (dithoracic) with the fusion involving the abdomen and pelvis. They can have two, three, or four arms and two or three legs.
— Pierro, A. Kiley E. Spitz L. Classification and Clinical Evaluation. Seminars in Pediatric Surgery 24 (2015) 207–211

There are two main kinds of conjoined twins: (i) symmetric conjoined twins (this is the kind discussed in today’s Daf Yomi) and (ii) heteropagus or parasitic twins. (A parasitic twin is a grossly abnormal fetus, or fetal parts, attached externally to a relatively normal twin. They are usually comprised of externally attached additional limbs but may also contain body parts. Today, after removing these additional parts and some plastic surgery, the surviving child usually appears normal.) The most likely kind of conjoined twins that Peleimu asked about were parapagus twins. These may be born with two, three or four arms, and it is likely that in the Peleimu’s case they were born with only two arms.


One classification of conjoined twins. 1=thoracopagus, 2=omphalopagus, 3=pygopagus, 4=ischiopagus, 5=craniopagus, 6=parapagus, 7=cephalopagus, 8=rachipagus. From Pierro A. Kiley E. Spitz, L. Classification and clinical evaluation. Seminars in Pediat…

One classification of conjoined twins. 1=thoracopagus, 2=omphalopagus, 3=pygopagus, 4=ischiopagus, 5=craniopagus, 6=parapagus, 7=cephalopagus, 8=rachipagus. From Pierro A. Kiley E. Spitz, L. Classification and clinical evaluation. Seminars in Pediatric Surgery 24 (2015): 207–211.

Conjoined twins in later rabbinic literature

Rabbi Yaakov Hagiz (1620–1674) was born in Fez, Morocco. For a while he lived in Italy, and around 1657 he settled in Jerusalem, where he founded a yeshivah. He described a case of conjoined male twins that he had seen.

שו"ת הלכות קטנות חלק א סימן רמה

זכורני שראיתי במדינות איטלייא גוי א' כבן כ"ה שנים שנולד דבוק עם תאומו עד הטבור חזה כנגד חזה ושם נדבקו והוא היה הולך ושלם כשאר בני אדם וראש הקטן מוטה לצד א' ורגליו תלויות ומגיעות עד ארכובותיו של גדול ולא היה בו הרגשה כלל אלא כאבר שנתבטל חושו ונתקיים כך כמה שנים עם תאומו. נסתפקו ההורגו מאי ואם מלין אותו ומהיכן הוא מתקיים מה שמתקיים צ"ל שטבורו דבוק עם של תאומו והכבד של אחיו שולח דם דרך שריון לכבד שלו ומשם ניזון כמו במעי אמו: ואפשר לדונו כדין גוסס ומלין אותו וממעט חלק ירושה ולכל דבר דינו כגוסס ואם יברך משנה הבריות כתבתי בפי' הש"ע דעל הגדול אין לברך ועל הקטן אומר דיין האמת כי רוב גוססים למיתה

A certain gentile, about twenty-five years old, who was born with a twin joined from his chest to his abdomen…who was able to walk normally like any other person. The head of the smaller twin was tilted to one side and his feet hung down and reached the thighs of the larger twin…it is possible to view the smaller twin as a goses [in the throws of death]…the blessing “he who creates different creatures”(משנה הבריות) is not to be made seeing the larger twin, but on seeing the smaller twin one should make the blessing “he who is the true judge” (דיין האמת)

Another eyewitness account of conjoined twins was recorded by Rabbi Jacob ben Joseph Reischer (~1670-1733). He served in various rabbinical positions in Prague, Worms, and Metz. In his book of responsa, Shevut Yaakov, (Vol 1 no. 4) he was asked about “an entirely new thing” brought from abroad and seen over the winter of 1708:

Two Gentile male twins joined at their skull. Each had all his limbs and feeling in them, like any other person…their faces were joined at the side, meaning that the left ear of one was next to the right ear of the other…from behind it appeared as if there was only a single extremely wide head. The rest of their bodies were quite separate; each would suckle and eat and drink and speak and feel by himself. They were more than a year old. I saw this with my own eyes and I made the correct blessing when I saw them..

Conjoined brothers from Nuremberg Chronicle (1493). From here.

Conjoined brothers from Nuremberg Chronicle (1493). From here.

…I was asked what would happen if, God forbid, there was such a case among the Jews…the case discussed in Menachot 37 is quite different from this one….Here there are two separate bodies…and there is nothing new in this, for this is what happened when the world was created…as stated in the Talmud in Berachot and in Eruvin. And the Midrash tells us that he [Adam] was created with two faces, as it states (Gen 5:2): “ זכר ונקבה בראם ויקרא שמם אדם - male and female he created them, and he called them Adam” …Since they are clearly two people each requires to put on the head tefillin (phylacteries), and place it between their own eyes. However they may not marry for there is a question of the prohibition against adultery, for they must sleep together in one bed. It is also forbidden for one to have intercourse because the other is watching… and may the Merciful One deliver us from all the odd and deformed creatures…

The Case in Menachot, and the Hensel twins

In 2002 Michael Barilan from the Meir Hospital and the Sackler School of Medicine in Tel Aviv, published a lengthy paper (Head Counting and Heart Counting) which questioned the assumption that a conjoined twin’s natural interest and wish is separation. “Too often” he wrote, “we tend to oversimplify bioethical problems and see them as a zero-sum game between rival individuals. Conjoinment challenges our sense of selfhood and identity. Rising to this challenge may refresh many commonplace notions about individuality, identity, and being with other people as a fundamental manifestation of being alive as human beings.”

Abby and Brittany Hensel. From here.

Abby and Brittany Hensel. From here.

Abby and Brittany Hensel are a perfect example of Barilan’s thesis. Born in 1990 in Minnesota, their parents decided not to seperate them at birth after learning that the chances of either surviving such an operation was extremely low. They have a single body and each controls the arms and leg on her side. They learned to walk at a normal age, graduated high school in 2008 and although each twin had to take her own test, they have driver’s licenses (and you can watch them driving here). The twins featured in a three part reality show on TLC in 2012, which later aired on the BBC. It featured their graduation from Bethel University, subsequent job search, and their travels in Europe. Their story, and those of many other unseparated twins, demonstrates that conjoined people may lead loving, meaningful and fulfilling lives together, whether or not they decide to don tefillin each day.

Both modern canon law and common law determine human individuation by the head. Possibly they had better count hearts. Head-counting is close to a Cartesian view of the soul as a distinct entity that is anchored in the head but not directly engaged with the human body. The Cartesian body is related to its mind as chattel to owner, thus promoting the economic language of division and distribution of lives and limbs...Heart-counting isless metaphysically ambitious or economically domineering and is more attuned to the practical constraints of embodied life, particularly of social beings.
— Y. Michael Barilan. Head-Counting vs. Heart-Counting: An Examination of the Recent Case of the Conjoined Twins from Malta. Perspectives in Biology and Medicine, 2002. 45; 4; 593-603.
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