Ephraim from Jerusalem wrote:
Dear Rabbi,
Time magazine (March 25, '96) had an article about a six-year old girl, or two six-year old girls rather, with two heads and one body. They're like 2 totally different people with different personalities and preferences. They have separate urges to eat, sleep and go to the bathroom. What if anything does Judaism says about such a situation. Is there any source in the Talmud that talks about this? Would they be considered one person or two?
Dear Ephraim,
Ever hear the phrase, 'Nothing's new under the sun?'
The Talmud records an exchange in which Phlimo asked Rabbi Yehuda HaNasi, "A person with two heads, upon which head does he place the tefillin?" Rabbi Yehuda thought Phlimo was merely jesting, when suddenly someone arrived and announced, "My wife had a baby with two heads! How much must I give for the redemption of the first-born?"
The Talmud concludes that the father must give double the normal amount. The Torah says the firstborn must be redeemed at "five sela'im per head." So here, where there are two heads, the father must give ten sela'im.
From the above, you can't necessarily extrapolate to other cases, because there are two opposite ways to understand it:
The Zohar records a tradition about the descendants of Cain, stating that they were born with two heads.
Actual instances of conjoined twins are found in the works Sha'ar HaShamayim (Ralbag 1547), Cheshek Shlomo (1773) and Shvut Yaakov (Rabbi Yaakov Reisher of Prague, 1739) and others.
The Shvut Yaakov himself saw twin boys, normal in all ways, but whose heads were joined side by side. In such a case, he writes, they are certainly separate people. He distinguishes between this case and the case in the Talmud where the two heads share one body.
There's really nothing new under the sun: Adam and Eve, says the Talmud, were created as a single male/female being with two faces. The subsequent creation of Eve was actually the splitting of the male and female into two separate parts!
Sources:
Three members of the Jewish People whose names are mentioned in Torah (and were alive at the time) did not go out of Egypt during the Exodus. Who are they?