Leviticus 20:19-21

You shall not uncover the nakedness of (have intimate relations with) your mother’s sister or your father’s sister, for such a one has uncovered his blood relative; they will bear their guilt. If there is a man who lies [intimately] with his uncle’s wife, he has uncovered his uncle’s nakedness; they will bear their sin. They will die childless. If a man takes his brother’s wife, it is a hated and unclean thing; he has uncovered his brother’s nakedness. They will be childless.