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