Sexual intercourse between close blood relatives, including brothers and sisters, parents and children, grandparents and grandchildren, or aunts or uncles with nephews or nieces. it is a crime in all states, even if consensual by both parties. however, it is often co-existent with sexual abuse since usually the younger person is a victim of the predatory sexual activities of an older relative. recently, it has drawn more attention as people began talking about the “silent crime,” which is often covered up by a wife fearful of losing a husband, or the memory has been suppressed by the youthful victims. one problem is that on the surface the family may appear to be “all-american” while abusive incest continues. in 18 states incest also includes copulation or cohabitation between first cousins, but the majority of jurisdictions permit marriage between such cousins. the rationale for prohibition of first cousin marriages is not so much moral as the fear of proliferation of mental or physical weakness due to the joining of recessive family genes carrying such weaknesses.