RSA 639:2 Incest.

I. A person is guilty of a class B felony if he or she marries or engages in sexual penetration as defined in RSA 632-A:1, V, or lives together with, under the representation of being married, a person 18 years or older whom he or she knows to be his or her ancestor, descendant, brother, or sister, of the whole or half blood, or an uncle, aunt, nephew, or niece; provided, however, that no person under the age of 18 shall be liable under this section if the other party is at least 3 years older at the time of the act. The relationships referred to herein include blood relationships without regard to legitimacy, stepchildren, and relationships of parent and child by adoption.
II. In cases of alleged incest where the victim is under the age of 18 when the alleged offense occurred