Hilchos Issurei Biah 2:14

If a man’s father or son marries a woman, that man may marry her daughter or mother as has already been discussed. One is permitted to marry the wife of his brother’s son. A man may be married to a woman and her sister’s daughter or her brother’s daughter simultaneously. The Sages consider it meritorious for a man to marry his sister’s daughter as per Isaiah 58:7, “Don’t hide yourself from your own flesh.” This also applies to the daughter of one’s brother.

Hilchos Issurei Biah 3:1

If a man is intimate with a minor’s wife, he is not liable; this is true even of a yevama with whom a nine-year-old performed yibum (levirate marriage). The same is true if a man is intimate with the wife of a person with congenital deafness or who lacks mental competence, as well as the wife of a person of indeterminate gender, a hermaphrodite, a woman with congenital deafness or who lacks mental competence married to a mentally-sound man, a woman whose betrothal is in doubt and a woman whose divorce is in doubt. In all of these cases, one is not liable but if they violated willfully, they are subject to stripes for acting rebelliously.