The list of marriages forbidden by Jewish law is found in the book of Leviticus (18: 16–30; 20: 9–22). The union of a sister and brother or mother and son and the other instances mentioned have no validity whatsoever, so that if such a ‘marriage’ has taken place no divorce is required to dissolve it. While a nephew may not marry his aunt, a niece may marry her uncle and the marriage of first cousins to one another is allowed. A man's stepson may marry his wife's stepdaughter and his stepdaughter his wife's stepson since there is no blood relationship. The marriage of a mamzer to a Jew is not allowed but a mamzer may marry a mamzeret. The children of such a marriage, however, would be mamzerim. A Kohen may not marry a divorcee. A man may not marry his wife's sister while both are alive but may do so after the death of his wife.
Subjects: Judaism and Jewish Studies.