Why were marriages between brothers and sisters allowed in the times of Noah but not now?
The prohibition of marriages between brothers and sisters is found in Leviticus 18:6-9, together with prohibition of marriages with other family members and close relatives. These prohibitions still apply to Christians, since the apostle Paul disciplined a member of the Corinthian church for marrying his widowed step-mother (1 Corinthians 5:1) and he called this relationship an immoral one. Today, such relationships are known as incest, and are disapproved by the public. However, in the times before Moses, there was some tolerance for such marriages. e.g. the children of Adam and Eve probably had to marry each other, since there was no one else for them to marry. Hence Cain and Seth must have married their own sisters and had children by them. God permitted this only at the beginning, out of necessity. As more and more people lived on earth, there was no more need for this practice, and hence it became sinful for anyone to marry his own sister. Today, it is also known that incestuous r
