Leviticus 20:19-21

You shall also not uncover the nakedness of your mother’s sister or of your father’s sister, for such a one has made naked his blood relative; they will bear their guilt. If there is a man who lies with his uncle’s wife he has uncovered his uncle’s nakedness; they will bear their sin. They will die childless. If there is a man who takes his brother’s wife, it is abhorrent; he has uncovered his brother’s nakedness. They will be childless.