The following women are prohibited for you in marriage: Your mothers, daughters, sisters, father's sisters, mother's sisters, brother's daughters, sister's daughters, foster-mothers who have ever nursed you, foster-sisters, your wives' mothers, your step-daughters unless you have divorced their mother without being intimate with her. Also forbidden are women who have ever been the wives of your sons. You are not allowed to keep two sisters in wedlock at one time except what has already happened in the past. Allah is Forgiving, Merciful.