Marriages Prohibited by In-Law Relationships

1-The mother-in-law: Marriage to the wife's mother is permanently prohibited from the time a man enters into a marriage contract with a woman, whether he and his wife have engaged in sexual intercourse or not. The act of marriage itself gives the mother-in-law the same status as the mother.

2-The step-daughter: A man cannot marry his step-daughter (his wife's daughter by a previous marriage) if sexual intercourse has taken place with her mother, his wife. However, if a man divorces his wife without having had intercourse with her, it is permissible for him to marry her daughter by a previous marriage.

3- The daughter-in-law: That is, the wife of the real son, not that of the adopted son. In fact, Islam abolished the permissibility of the system of legal, formalized adoption, because this is contrary to fact and to reality, resulting in the prohibiting of what is essentially halal and the permitting of what is essentially haram. Allah Ta'ala says: ...Nor has He made your sons by adoption your (real) sons. Those are simply words from your mouths....(33:4) meaning that it is merely an expression of the language which does not alter reality nor transform an outsider to the family into a blood relative.

These three types of female relatives are forbidden in marriage in order that peaceful relationships may be maintained among the in laws.