• Generally, with slight variations from jurisdiction to jurisdiction, the law forbids marriages between all persons lineally related and within the third civil-law degree of relationship. That is, aunt–nephew and uncle–niece relations are prohibited. Prohibited degrees are also known as Levitical degrees, since the incest prohibition is pronounced in the Bible in Leviticus 18:6–18.
— Also termed forbidden degree. [Cases: Marriage 10. C.J.S. Marriage § 17.]