Yevamos 14:3-4

Yevamos 14:3

Let’s say that two brother with congenital deafness are married to two sisters with congenital deafness, or to two sisters who have all their senses, or to two sisters, one of whom has congenital deafness and the other of whom has all her senses; or two sisters with congenital deafness are married to two brothers with all their senses, or to two brothers with congenital deafness, or to two brothers, one of whom has congenital deafness and the other of whom has all his senses. In all of these cases, these women are exempt from yibum and chalitzah. If the women were unrelated, they perform yibum and if they want, they may divorce (with a get, but chalitzah would not be effective).

Yevamos 14:4

If two brothers, one of whom has congenital deafness and the other of whom has all his senses, are married to two sisters who have all their senses, then the brother with congenital deafness dies, what does the brother with all his senses do? The widow is exempt because she is his wife’s sister. If the brother with all his senses dies, what does the brother with congenital deafness do? He must divorce his wife with a get (because his Biblical-level yibum connection trumps his rabbinic-level marriage) and he may never marry his brother’s widow (as she is the sister of a woman he divorced).