Is it wrong to have a romantic relationship with a close relative?

Response

The prohibited relationships in the Old Testament Law are detailed in Leviticus chapter 18, verses 6–18. In this passage, the Israelites are instructed not to engage in incest, which is considered a sinful act “Do not defile yourselves in any of these ways, for by all these practices the nations I am casting out before you have defiled themselves”, (Leviticus 18:24). The law specifies relationships, whether through marriage or not, that God deemed as incestuous. An Israelite man was prohibited from marrying or having relations with the following individuals:

His mother

His step-parent

His sister or half-sister (and potentially a step-sister not biologically related but raised as his parent’s daughter)

His aunt

His daughter-in-law

His sister-in-law, as long as his wife was alive “And you shall not take a woman as a rival wife to her sister, uncovering her nakedness while her sister is still alive”, (Leviticus 18:18)

Interestingly, the Bible does not explicitly forbid marriage between cousins. However, the other relationships mentioned above are considered immoral.

In the early days of humanity, before the law was given, there was a necessity for marriages among close relatives due to the limited number of human beings. Adam and Eve’s children, out of necessity, married their siblings. Even during that time, marriage between a parent and child was not permitted, as implied in Genesis 2:24: “That is why a man leaves his father and mother and is united to his wife, and they become one flesh.” A man was meant to leave his mother, not marry her.

As the population on earth increased significantly, there was no longer a need for intermarriage among relatives. In the early days of humanity, the human genetic code remained uncorrupted.To the extent that it is today. Therefore, marriages between close relatives carried little risk of genetic abnormalities in the children they produced. Once the human race expanded and, due to sin, the human genetic code grew more corrupt, God commanded against the marriage of close relatives.

There is nothing inherently wrong with marrying a first cousin or other, more distant relative. There are other considerations, though. One is the civil law in the place where we live: many places disallow marriage between first cousins, and the Bible commands us to obey the laws of the nation we live in (Romans 13:1-6).

While Christians are no longer under the Law of Moses, the moral principles still stand. That means that the relationships listed in Leviticus 18 are still immoral. No one should marry a sibling or a parent. The only moral exception to the list is that of marriage to an in-law after the death of a spouse.