Incest is marriage or sexual relations between close relatives. The criminal offense of incest may also be known as prohibited sexual conduct. Laws vary from state to state, but incest laws generally prohibit marriage or sexual relations between (1) a person’s ancestor or descendant by blood or adoption; (2) a person’s current or former stepchild or stepparent; (3) a person’s parent’s brother or sister of the whole or half blood; (4) a person’s brother or sister of the whole or half blood or by adoption; (5) the children of a person’s brother or sister of the whole or half blood, or by adoption; or (6) the son or daughter of a person’s aunt or uncle of the whole or half blood or by adoption.

Lack of consent to sexual relations between such relatives is not an element of the crime, and persons may be guilty of the crime even if both parties consented.

Laws regarding incest or prohibited sexual contact vary from state to state and are generally located in a state’s statutes—often in the penal or criminal code. The crime is a felony offense in many states, with potential punishment of significant jail or prison time.

In South Carolina, incest is legally defined as sexual intercourse between persons who are within a certain degree of kinship to each other. The state's laws prohibit marriage or sexual relations between parents and children, siblings, and various other close relatives, whether by blood or adoption. Specifically, South Carolina law prohibits sexual relations between a person and their ancestor or descendant, stepchild or stepparent, sibling of the whole or half blood, or by adoption, and between uncles, aunts, nieces, and nephews. Consent is not a defense to a charge of incest in South Carolina, meaning that the crime can be prosecuted even if both parties consented to the sexual relationship. Incest is considered a felony in South Carolina, and those convicted can face severe penalties, including imprisonment.