Q. When did it become unlawful to marry family members? There must have been some point in time where ‘all in the family’ relations were declared to be against God’s law, when it was understood to be a sin. Is there some place in the Bible where this is noted, or was it within the scope of the adultery commandment?
A. Forbidden sexual relations were first listed in Leviticus 18 during the time of the wilderness wanderings. They include incest, bestiality, homosexuality and child sacrifice as well as other unlawful sexual conduct. Prohibiting sexual relations between family members effectively put an end to “all in the family” marriages.