157 Yevamot 11/1-3

(1) A man may lawfully marry the near relatives of a woman whom he has violated or seduced, but he who has either violated or seduced the near relatives of his wife, has become guilty of incest. A man may marry a woman who had been violated or seduced by his father, or one who had been thus treated by his son. Rabbi Yehudah prohibits a son to marry a woman who had been violated or seduced by his father.

(2) When the sons of a female proselyte have adopted the Jewish faith at the same time with their mother [and one of them dies without issue], his brother is not bound to yibum, nor to receive Chalitzah [from the widow of his deceased brother]. Even when the first was conceived before she participated in the holiness [of the Jewish community], but was born under the Holy covenant, and that the other brother was both conceived and born under the Holy covenant. The same regulation applies to a bondwoman whose children were manumitted along with her.

(3) When the sons of five women have become intermixed with each other [and each woman has another son, of whose identity she is certain], when these mixed sons have grown up, married, and died [without issue], then four of the surviving brothers shall cause the widow of one to perform Chalitzah to them, and the fifth brother may marry the widow; then shall he and three other brothers receive Chalitzah from another widow, whom another brother may marry by yibum[and in the same manner with the remainder], so that each of these widows must perform the ceremony of Chalitzah four times, and can then be married by Yeboom.