Yevamot

'My  paternal, but not my maternal brother; and he is the husband of my mother and I am the daughter of his wife'!  — Rami b. Hama said: Such [a relationship is] not [legally possible] according to the ruling of R. Judah in our Mishnah. 'He  whom I carry on my shoulder is my brother and my son and I am his sister'? — This is possible when an idolater cohabited with his daughter'. 'Greetings  to you my son; I am the daughter of your sister'? — This is possible where an idolater cohabited with his daughter's daughter. 'Ye  water-drawers,  we shall ask you  a riddle that defies solution: He whom I carry is my son and I am the daughter of his brother'? — This is possible where an idolater cohabited with the daughter of his son. 'Woe,  woe, for my brother who is my father; he is my husband and the son of my husband; he is the husband of my mother and I am the daughter of his wife; and he provides no food for his orphan brothers, the children of his daughter'? — This is possible when an idolater cohabited with his mother and begot from her a daughter; then he cohabited with that daughter; and then the grandfather  cohabited with her  and begot from her sons. 'I  and you are brother and sister,  I and your father are brother and sister, and I and your mother are sisters'? — This is possible where an idolater cohabited with his mother and from her begot two daughters, and then he cohabited with one of these and begot from her a son. When the sons's mother's sister  carries  him  she addresses him thus. 'I  and you are the children of sisters,  I and your father are the children of brothers, and I and your mother are the children of brothers'? — This indeed is possible also in the case of a lawful marriage; where, for instance, Reuben had two daughters, and Simeon  came and married one of them, and then came the son of Levi  and married the other. The son of Simeon can thus  address the son of the son of Levi. MISHNAH. THE SONS OF A FEMALE PROSELYTE WHO BECOME PROSELYTES TOGETHER WITH HER NEITHER  PARTICIPATE IN HALIZAH NOR CONTRACT LEVIRATE MARRIAGE, EVEN IF THE ONE WAS NOT CONCEIVED IN HOLINESS.  BUT WAS BORN IN HOLINESS,  AND THE OTHER WAS BOTH CONCEIVED AND BORN IN HOLINESS. SO ALSO [IS THE LAW] WHERE THE SONS OF A BONDWOMAN WERE EMANCIPATED TOGETHER WITH HER. GEMARA. When the sons of the bondwoman Yudan were emancipated. R. Aha b. Jacob permitted them to marry one another's wives.  Said Raba to him: But R. Shesheth forbade [such marriages]. The other replied: He forbade, but I allow. [In respect of proselyte brothers] from the same father and not from the same mother, there is no difference of opinion  that this  is permitted;  [in respect of brothers] from the same mother and not from the same father, there is no difference of opinion  that this  is forbidden.  They differ only [in respect of proselytes whose brotherhood is] both paternal and maternal. He  who permits it  [does so because children are] ascribed to their father, since they are spoken of as 'the children of such and such a man'.  R. Shesheth, however, [holds that they] are also spoken of as 'the children of such and such a woman'. Another reading: R. Aha b. Jacob disputed [the illegality of marriage]  even in respect of maternal brothers. And what is his reason? — Because a man who has become a proselyte is like a child newly born. We learned, THE SONS OF A FEMALE PROSELYTE WHO BECAME PROSELYTES TOGETHER WITH HER NEITHER PARTICIPATE IN HALIZAH NOR CONTRACT THE LEVIRATE MARRIAGE, is not the reason  because they are forbidden [to marry a brother's wife]!  — No; it is because [the widow] is not subject to the law of halizah and levirate marriage.  She is permitted, however, to strangers.  and the brothers also are permitted[to marry her]. But, surely, it was stated EVEN! Now were you to admit that [the brothers] are forbidden.  one could well justify the expression of EVEN: EVEN IF THE ONE WAS NOT CONCEIVED IN HOLINESS BUT WAS BORN IN HOLINESS. AND THE OTHER WAS BOTH CONCEIVED AND BORN IN HOLINESS, [so that the two might well be regarded] as [the sons of] two mothers,  they are nevertheless forbidden; if you maintain, however, that they are permitted,  what [can be the purport of] EVEN!  — Even though the birth of both was in holiness, and people might mistake  them for Israelites,  [the widow] is nevertheless permitted [to marry a stranger]. Others read: Logical reasoning also supports the view that they are permitted,  since the expression EVEN was used. For, if you grant that they are permitted  it is quite correct to say EVEN: Even though the birth of both was in holiness and people might mistake  them for Israelites.  they are nevertheless permitted;  if, however, you maintain that they are for bidden  what [can be the purport of] EVEN!  — EVEN IF THE ONE WAS NOT CONCEIVED IN HOLINESS BUT WAS BORN IN HOLINESS, AND THE OTHER WAS BOTH CONCEIVED AND BORN IN HOLINESS [so that they might well be regarded] as [the sons of] two mothers,  they are nevertheless forbidden. Come and hear: Twin brothers who were proselytes, and similarly if they were emancipated slaves,  may neither participate in halizah nor contract levirate marriage, nor are they guilty [of a punishable offence] for [marrying] a brother's wife.  If however, they were not conceived in holiness but were born in holiness, they neither participate in halizah nor contract levirate marriage  but are guilty [of a punishable offence]  for [marrying] a brother's wife.  If they were both conceived and born in holiness, they are regarded as Israelites in all respects. At all events, it was stated that they are not 'guilty [of a punishable offence] for [marrying] a brother's wife'; [from which it follows that] no punishable offence is incurred