incest

Sexual relations between persons who are so closely related that their marriage is illegal or forbidden by custom.

The crime of sexual relations with a person defined by statute as too closely related.

The offense of cohabitation or sexual commerce between persons related within the degrees wherein marriage is prohibited by the law or established usage of a country. In this offense illegitimate consanguinity is of the same effect as legitimate.

The holding, by a vicar or other beneficiary, of two benefices, one of which depends upon the collation of the other.

The crime of cohabitation or sexual intercourse between persons related within the degrees wherein marriage is prohibited by law

The act of a vicar, or other beneficiary, who holds two benefices, the one depending on the collation of the other.

Sexual relations between close relatives (too closely related to be legally married), usually considered taboo, and a crime in many jurisdictions.

sexual intercourse between persons too closely related to marry (as between a parent and a child)