Incest is defined as "sexual intercourse between people who are very closely related." Depending on the jurisdiction, you may be subject to more detailed. Incest is as old as the human race. In fact, the human population wouldn't have thrived had people back then didn't engage in incest. Today. Most people find incest unacceptable, and there are compelling reasons for such a position: (1) culturally and traditionally, incest is largely.