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Legality of incest

Legality of sexual relationships between family members

  • 21 min read
  • 8 chapters

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Through Marriage, Age of consent and Adoption

Incest laws may involve restrictions on marriage, which also vary between jurisdictions. When incest involves an adult and a child (under the age of consent) it is considered to be a form of child sexual abuse.

Degrees of relationship

Laws regarding incest are sometimes expressed in terms of degrees of relationship. The degree of relationship is calculated by adding the number of generations back to a closest common ancestor of each individual. Consanguinity (but not affinity) relationships may be summarized as follows:

Most laws regarding prohibited degree of kinship concern relations of r = 25% or higher, while most permit unions of individuals with r = 12.5% or lower. In 24 states of the United States, cousin marriages are prohibited. Also, most laws make no provision for the rare case of marriage between double first cousins. Incest laws may also include prohibitions of unions between biologically unrelated individuals if there is a close legal relationship, such as adoption or step relations.

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