Incest taboo

An incest taboo is any cultural rule or norm that prohibits sexual relations between closely related persons. All human cultures have norms that exclude certain close relatives from those considered suitable or permissible sexual or marriage partners, making such relationships taboo. However, different norms exist among cultures as to which blood relations are permissible as sexual partners and which are not. The sexual relations between related persons which are subject to the taboo are called incestuous relationships.