Leviticus 20:19-21

“ ‘Do not have sexual relations with your mother’s sister or your father’s sister, because that would shame a close relative. Both of you are guilty of this sin. “ ‘If a man has sexual relations with his uncle’s wife, he has shamed his uncle. That man and his uncle’s wife will die without children; they are guilty of sin. “ ‘It is unclean for a man to marry his brother’s wife. That man has shamed his brother, and they will have no children.