But later, in the Law given through Moses, such marriage unions were specifically forbidden. (Lev. 18:9, 11)

But about 2,500 years after Adam became a sinner, God prohibited incestuous marriage. This served to safeguard the offspring and it elevated the sexual morality of Jehovah’s servants above that of people around them who were then engaging in all manner of depraved practices.—See Leviticus 18:2-18.