What offense is committed when a man has sexual relations with his sister?

The offense committed when a man has sexual relations with his sister is classified as incest. Incest refers specifically to sexual relations between family members who are too closely related to be legally allowed to marry. This typically includes relationships between siblings, parents and children, and other close relatives as specified by law.

Prohibited sexual conduct is a broader term that can encompass various forms of sexual relations that are restricted by law due to familial relationships, but the specific act of a man having sexual relations with his sister clearly falls under the definition of incest. Understanding the distinction between these terms is crucial, as legal definitions can vary by jurisdiction, but in many legal systems, incest is explicitly designated with defined penalties.

By recognizing that the relationship is familial and the legal implications that accompany such interactions, it becomes clear that incest is the correct identification of the offense.