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Siamese Twins in Halacha

Did you know that a pair of Siamese twins was born when the nation wandered in the desert? Hints for this can be found in the words of this week’s parasha. Since Siamese twins don’t usually survive too long, how long did those who were born in the desert survive? And what does the Gemara have to say about this rare phenomenon? Halachically, are Siamese twins considered one person or two? How much does their father pay to redeem them if they are firstborn males? What is their life expectancy?

What happens if one twin is essentially living at the expense of the other to the extent that if one is not killed, both will die – is the dependent twin considered a rodef of the healthier one, or is it forbidden to kill him?

This week’s article will also discuss other freaks of nature — living creatures outside the atmosphere, how they look, and their possibility of integrating in Earth-society.

Shlomo Hamelech seems to have been presented with a case of Siamese twins embroiled in an inheritance feud. How did Shlomo Hamelech resolve this issue?

Does one recite a special blessing upon seeing Siamese twins, and if yes what is it?

We will discuss these in this article.


This week’s parasha starts out with one of the censuses conducted in the Jewish nation. Hashem commands: “Take the sum of all the congregation of the children of Yisrael, by families following their fathers’ houses; a head count of every male according to the number of their names” (Bamidbar 1:2). Throughout this census the Torah repeatedly stresses the counting should done by a head count. Later on, in the census of the tribe of Levi, there is no such emphasis. The Chasam Sofer mentions an explanation he heard from Rabbi Shmuel of Krakow:

The Gemara (Menachos 37a) rules that a two-headed firstborn male must be redeemed with 10 slaim (a silver coin) instead of the standard five. (1 Torah-shekel was worth 1 sela). This is derived from the pasuk in this week’s parasha: “You shall take five shekels per head” (Bamidbar 3:47). If this had been written with regard to the tribe of Levi, a two-headed one-month old baby would have been counted as two people. Therefore, in the Levi census there is no mention of head counting. But with the rest of the nation, since they were counted only from 20 and up, and a two-headed person would not have lived till the age of 20, we do find the mention of a headcount because there is no fear of counting a two-headed person as two people.

The Chasam Sofer argues with Rabbi Shmuel of Krakow on this point – in his opinion a two-headed human can reach the age of 20. Therefore, he explains, according to this explanation, when the Jewish nation was in the desert there was a two-headed person, for whom the Torah had to instruct to specifically conduct a headcount. Hence, Siamese twins are counted as two separate people. Amongst the tribe of Levi, though, there were no Siamese twins.

This week’s article will discuss these intriguing cases in light of the halacha.

Siamese Twins in the Gemara

The Gemara in Menachos (37a) describes an interesting case that was presented to the Sages:

Rabbi Peleimu raised a dilemma before Rabbi Yehuda HaNasi: In the case of one who has two heads, on which of them does he don tefillin? Rabbi Yehuda HaNasi said to him: Either leave 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? An elder came and taught him: You are obligated to give him ten sla’im, five for each head.

The man who came to ask about his newborn twins served as a heavenly hint to Rabbi Yehuda HaNasi not to be upset with his student because the question was a legitimate one that required a decision. The Gemara, however, does not provide details of the answer to the question he asked – on which head do Siamese twins lay tefillin.

Interestingly, the Tosefos in Chulin (6a) note that when the Gemara writes “a certain elder” it is always Eliyahu Hanavi. He appeared in the Beis Midrash to teach the halacha of Siamese twins as it appears in this week’s parasha: “You shall take five shekels per head” – for every head one must pay the kohen five shekels, or sla’im.


The Tosefos (Menachos 37a) write that while humans in this word do not have two heads, outside of this world there are creatures that do. The Tosefos mention a Midrash:

Ashmedai, the king of the sheidim (ghosts) presented Shlomo Hamelech with a two-headed human from Tevel an underground land. This person remained in Eretz Yisroel, married a regular woman, and had children. Some of them were two-headed like him, and some were normal, like his wife. His wealth prospered, and after his death, the sons came to Shlomo Hamelech to determine how to divide their inheritance – is it divided by the head, in which case the two-headed ones would inherit double, or should it go by the body?

The Tosefos do not mention what Shlomo Hamelech’s ruling was, but the Shitta Mekubetzes (247:18) quotes the story as it appears in the Midrash – Shlomo Hamelech ordered boiling water poured on one of the heads and the second head began shouting. This was proof enough that they possessed one nervous system and were actually one person. As a result, they only received one portion of the inheritance.

One Person or Two

In light to Shlomo Hamelech’s ruling it would seem that Siamese twins are one person with two heads. (This also explains why the two-headed man could marry and his wife was not considered married to two people.)

Rabbi Chaim Soloveichick (Chidushei Hagrach, Menachos 37a) proves that a head without a body is exempted from the obligation of Pidyon Haben and a two headed child is essentially one firstborn, not two. However, since the Torah determines that the Kohen must be paid five slaim for every head, if the firstborn has two skulls, his father must pay for each of them separately. (Rashi explains that they are two firstborns since they entered the world at exactly the same moment.)

The Shevus Yaakov (volume I, res. 4) however, maintains that a two headed person is considered two people for all Torah-related purposes. He adds various details and explains why they should not be permitted to marry.

Two-Headed Man – Siamese Twins?

The Keren Ora (Menachos 37a) explains that although there was such a person in Shlomo Hamelech’s time, he was brought from the netherworld and therefore not considered human and his conversion is meaningless. This kind of creature cannot exist in our world, as the Tosefos explain. The Sefas Emes (ibid) writes that two-headed babies seen today are actually twins who due to faulty cell division were joined during pregnancy. The second skull is inviable and whatever life he has is received from the body of the first. The only reason one mustpay the Kohen double for redeeming this kind of firstborn child is because there is a gzeiras hakasuv – a ruling of the pasuk — that every skull requires redemption of 5 sla’im.

This seems to indicate that there are two distinct creatures: the two-headed man mentioned in the Midrash does not exist in this world, although there is an indication that it exists in other worlds. This creature, according to the Keren Ora, is not obligated to perform mitzvos and is not considered human. The case of Siamese twins, though, which although rare, is not unheard of, may be considered two separate humans, and each case must be judged separately.

Survival Rates

As we mentioned, Rabbi Shmuel of Krakow and the Chasam Sofer disagreed about a two-headed baby’s survival prospects. Rabbi Shmuel ruled that this baby is a treifa (a living being that cannot live for 12 months) which can be proven from the halachos of animal kashrus – the rule is that every animal that has an additional limb – if removal of that limb would render the animal treif, especially if it is a vital organ, the animal is a treifa even before removal of the organ or limb. A person who is born with an additional finger, for example, since without the finger he is not treif, the additional finger does not render him treif. However, one who has an additional heart, or even ventricle – since if he would not have a heart or any ventricle, he would not have been able to live, the additional heart or ventricle renders him a treifa. Therefore, a baby with an additional head – since the head is a vital organ whose general removal would end life – is considered treif.

Therefore, explains Rabbi Shmuel, while among the tribe of Levi, Siamese twins were possible because they were counted from the age of one month, amongst the rest of the nation, whereas they were counted from age 20, it was impossible that there were living Siamese twins.

However, according to the Chasam Sofer, while a two-headed human is considered treifa, the Rashba opines that the treifa ruling mentioned above refers to all treifos except additional limbs. Although there is a rule that an additional limb is counted as if it is missing and it is treif, the animal can live a long life.

In addition, the Maharshal writes that while a regular treifa does not live more than 12 months, there are exceptions who live longer.

Therefore, the Chasam Sofer asserts that while a two headed person has the status of a treifa, he may live a long life. The poskim record having seen such cases, and although their chances of survival are slim, they do exist, and some survive for longer periods of time.

One at the Expense of the Other

Most Siamese twins born today would not survive without being surgically separated. Most cases allow for only one of the twins to remain alive and leading halachic authorities have been consulted on the matter – which one should be saved. The basic question still remains – is it permissible at all to sacrifice one life to save another, or is this an act of direct murder?

Rabbi Moshe Feinstein zata”l was presented with a complex case of Siamese twins fused from the shoulder down who shared one six-chambered heart. All physicians called in to evaluate them agreed that both would die unless separated while one could be viable if the other would be killed during surgery. Rabbi Moshe Feinstein was closeted in his home for nearly two weeks exclusively dealing with this question. At the end he concluded that the smaller baby whose chances of survival upon separation were non-existent was ruled as a rodef of the larger baby, and they family went through with the surgery.

Rabbi Moshe Feinstein chose not publish his reasoning for this ruling, and it is not included in the Igros Moshe, perhaps intentionally – so no one would be able to learn from this case to other cases due to the intricacy of the ruling process and the chances of mistakes.

This debate could have had practical ramifications in the horrible tragedy in Meron if one live person was pinned down by a dying person on top of him – if he would have moved the upper person he had hope of surviving, but he might have caused him to die in the process. Although the higher person was lying on top of him due to no fault of his own, he was in a situation that may categorize him as a rodef of the people below him, in which case the lower people could do anything they had to do to save themselves, including killing people atop of them.

Obviously judging the situation is impossible, but for the theoretic halachic discussion, see Rabbi Shlomo Za’afrani (Or Torah, Teves-Shevat, 5766, chapter 35) where he explains Rabbi Moshe Feinstein’s possible reasoning.

To complete the discussion, we will mention the eye-witness account of the Halachos Ketanos (1620–1674) who saw twins in Italy fused at the chest and abdomen (Halachos Ketanos Vol. 1, ch. 245). While one twin lived for 25 years, his twin was attached to him to him like a lifeless appendage. He had a smaller head and legs, but his limbs didn’t atrophy because of the life it received from the body of the larger twin. The Halachos Ketanos debates if it would be permitted to kill the smaller twin and if the smaller twin needed to have a bris or not. He rules that the smaller twin has the status of a goses (a person in his death throes) and it is forbidden to kill him, despite his lack of feelings. (This does not contradict his possible status of rodef. It only is a source for the prohibition to kill him if we would not have the heter of rodef, despite his lack of a nervous system.)


The Shevus Yaakov (volume I, chapter 4) writes that he saw Siamese twins and recited the blessing of Meshane habriyos. The Halachos Ketanos (Vol. 1, ch. 245) disagrees and rules that one should not recite Meshane habriyos but Dayan ha’emes because the second twin is in his death throes. (When seeing a congenital birth defect the blessing of Meshane habriyos should be recited, while for a defect that occurred later the correct blessing is Dayan ha’emes.] Seemingly, the Halachos Ketanos was of the opinion that the failing twin was not a birth defect, and only when his development began deteriorating he received the status of a defect.

While the Shevus Yaakov ends his response with the words “Hashem should save us from such strange creatures”, the Halachos Ketanos recounts that he saw another freak of nature in Verona – two chicks connected on their side. Each had a separate body, and each ate and drank on its own. In this case, he ruled that should this chick survive 12 months it would graduate the treifa status and could be slaughtered together as one, without waiting between them. Seemingly, he saw this case as one creature. He adds that this may be how the original creation looked – -Adam and Chava were created connected. Perhaps, he writes, other creatures were created in a similar fashion.

Practically, the correct blessing upon seeing a strange creature such as Siamese twins is Meshane habriyos. This opinion appears in Piskei Teshuvos (Orech Chayim 225:20).

Rabbi Yitzchok Zilberstein (Chishukei Chemed, Eiruvin 18a) disagrees with the Kalachos Ketanos whether one is permitted to slaughter both chicks at the same time. He writes that for Adam and Chava, who were male and female, their connectedness was a virtue and they be considered one creature. However, Siamese twins, where two fetuses fuse into one, are two defective  bodies.

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