Sexual activity between close blood relatives, such as father-daughter, mother-son, or between siblings.
Sexual intercourse between members of the same family.
An act of sexual intercourse or other sexual activity with so close a relative, that it is illegal or culturally not allowed.
Sexual intercourse between persons closely related, usually so closely (e.g.. father and daughter) that legal marriage would be impossible.
Sexual contact between family members so closely related that marriage between them is legally or culturally barred. It most often occurs between older male relatives and minor-aged girls, and in most cultures is considered a form of child abuse.
Sexual activity between family members who are not husband and wife.
Sexual engagement among individuals who share such close familial ties that their legal union is prohibited is commonly referred to as incestuous relations.
Sexual relations involving individuals who are closely related, like a parent, child, sibling, uncle, aunt, nephew, niece, grandparent, or grandchild, is termed as incest. In the majority of societies, such behavior is considered illegal or taboo, and it is also against the doctrines of numerous religions.
Engaging in sexual activity between close relatives, such as siblings, is considered a criminal offense.