Laws vary by state, but generally, a person commits incest if he marries or engages in sexual intercourse with a person he knows to be, either legitimately or illegitimately:
- His ancestor or descendant by blood or adoption; or
- His brother or sister of the whole or half-blood or by adoption; or
- His stepchild or stepparent, while the marriage creating the relationship exists; or
- His aunt, uncle, nephew or niece of the whole or half-blood.
In some states incest also includes copulation or cohabitation between first cousins, but the majority of jurisdictions permit marriage between such cousins. Incest is a crime in all states, even if consensual by both parties. However, it is often related to sexual abuse since usually the younger person is a victim of the predatory sexual activities of an older relative. Statutes generally do not require the perpetrator to be a certain number of years older than the victim. Victims of incest and sexual abuse are strongly encouraged to talk to an adult they trust to protect themselves and others from further abuse and take advantage of the many resources available to help them heal.
Laws vary by state, but the following is an example of a state law dealing with aggravated incest:
"(a) Aggravated incest is:
- Marriage to a person who is under 18 years of age and who is known to the offender to be related to the offender as any of the following biological, step or adoptive relatives: Child, grandchild of any degree, brother, sister, half-brother, half-sister, uncle, aunt, nephew or niece; or
- (2) engaging in: (A) Otherwise lawful sexual intercourse or sodomy as defined by K.S.A. 21-3501 and amendments thereto; or (B) any lewd fondling, as described in subsection (a)(1) of K.S.A. 21-3503 and amendments thereto, with a person who is 16 or more years of age but under 18 years of age and who is known to the offender to be related to the offender as any of the following biological, step or adoptive relatives: Child, grandchild of any degree, brother, sister, half-brother, half-sister, uncle, aunt, nephew or niece.
(b) Aggravated incest as described in subsection (a)(2)(A) is a severity level 5, person felony. Aggravated incest as described in subsections (a)(1) and (a)(2)(B) is a severity level 7, person felony. "