Laws regarding incest (i.e. sexual activity between family members or close relatives) vary considerably between jurisdictions, and depend on the type of sexual activity and the nature of the family relationship of the parties involved, as well as the age and sex of the parties. Besides legal prohibitions and medical discouragements, at least some forms of incest are also socially taboo or frowned upon in most cultures around the world.
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:
Degree of relationshipRelationshipAverage DNAshared % Inbred strain 99%0identical twins; clones 100%1parent-offspring 50% 1full siblings 50% 23/4-siblings or sibling-cousins 37.5%2grandparent-grandchild 25% 2half-siblings 25%3aunt/uncle-nephew/niece 25% 4double first cousins 25% 3great grandparent-great grandchild 12.5% 4first cousins 12.5% 6quadruple second cousins 12.5% 6triple second cousins 9.38% 4half-first cousins 6.25% 5first cousins once removed 6.25% 6double second cousins 6.25% 6second cousins 3.13% 8third cousins 0.78% 10fourth cousins 0.20%This degree of relationship is usually indistinguishable from the relationship to a random individual within the same population (tribe, country, ethnic group).
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.
World map
Table Country Incest between consenting adults Prohibited relationships Penalties Afghanistan Illegal Lineal ancestors and descendants Full and half-siblings Death Albania Illegal Lineal ancestors and descendants Full and half-siblings Up to 7 years in prison Algeria Illegal Relatives in the descending or ascending line Full, consanguineous or uterine brothers and sisters A person and the child of one of his full, consanguineous or uterine brothers or sisters or with a descendant thereof The mother or the father and the husband or the wife, the widower or the widow of his child or of another of his descendants Stepmother or stepfather and the descendant of the other spouse Persons one of whom is the wife or husband of a brother or sister The penalty is ten (10) to twenty (20) years of imprisonment in the 1st and 2nd cases, five (5) years to ten (10) years of imprisonment in the 3rd, 4th and 5th cases and from two (2) years to five (5) years imprisonment in the 6th case Angola Legal Antigua and Barbuda Illegal Parent, child, brother, sister, grandparent, grandchild, uncle (by blood), niece, aunt (by blood) or nephew For life, if committed by an adult with a person under fourteen years of age For fifteen years, if committed by an adult with a person fourteen years of age or more For two years, if committed between minors fourteen years of age or more Argentina Legal Armenia Illegal Australia Illegal Varies by state Varies by state (up to life imprisonment in one state: Queensland) Austria Illegal (Penile-vaginal intercourse)/ Legal (other practices) Penile-vaginal intercourse between lineal ancestors and descendants Penile-vaginal intercourse between full and half-siblings Up to 1 year in prison or 720 "day-fines" for linear ancestors and descendants Up to 3 years in prison for linear ancestors, who have seduced their descendants
Up to 6 months in prison or 360 "day-fines" for siblings Azerbaijan Illegal Bahamas Illegal Parent, child, brother, sister, grandparent, grandchild, uncle (by blood), niece, aunt (by blood) or nephew If he is an adult who commits the offence with a minor, for life subject to, on a first conviction for the offence, a term of imprisonment of seven years, and in the case of a second or subsequent conviction for the offence, a term of imprisonment of fourteen years If he is an adult who commits the offence with another adult, for a term of ten years If he is a minor who commits the offence with another minor, for a term of two years Bangladesh Illegal Lineal ancestors and descendants Full and half-siblings Life imprisonment Barbados Illegal Parent, child, brother, sister, grandparent, grandchild, uncle (by blood), niece, aunt (by blood) or nephew If committed by an adult with a person under 14 years of age, for life If committed by an adult with a person 14 years of age or more, for 10 years If committed between minors 14 years of age or more, for 2 years Belarus Legal Belgium Legal Belize Illegal Granddaughter, daughter, sister, half-sister, mother, grandfather, father, brother, half-brother or son Imprisonment for seven years Benin Illegal Bhutan Illegal A person to whom the defendant is related by consanguinity or affinity in such a way that they cannot legally marry Bolivia Legal Bosnia and Herzegovina Illegal Botswana Illegal Grandchild, child, brother, sister or parentBotswana Penal Code, section 168. Up to 5 years in prison Brazil Legal Brunei Illegal Lineal ancestors and descendants Full and half-siblings Death (Syariah Penal Code) Up to ten years in prison (Secular Penal Code) Bulgaria Illegal Lineal ancestors and descendants Adopters and adopted persons Full and half-siblings Up to three years in prison Burkina Faso Illegal Cabo Verde Legal Cambodia Legal Canada Illegal Child/parent or grandchild/grandparent Full and half-siblings Up to 2 4 years in prison Central African Republic Legal Chile Illegal Consanguineal ancestors and descendants Consanguineal siblings From 61 days up to 3 years and 1 day in prison China Legal Colombia Illegal Consanguineal and adopted ancestors and descendants Consanguineal and adopted siblings From 16 up to 72 months in prison Costa Rica Legal Croatia Illegal Linear ancestors and descendants Full and half-siblingsUp to one year in prison Cuba Illegal Czech Republic Illegal Lineal ancestors and descendants Siblings Related by blood or adoption Up to three years in prison Democratic Republic of the Congo Legal Denmark Illegal Lineal ancestors and descendants Full and half-siblings Up to six years in prison (direct line) Up to two years in prison (siblings) Dominica Illegal Parent and child Brother and sister, whether of the whole or the half blood, and whether the relationship is traced through lawful wedlock or not Uncle and niece or aunt and nephew Grandparent and grandchild For twenty-five years, if committed by an adult with a person under fourteen years of age For ten years, if committed by an adult with a person fourteen years of age or more For two years, if committed between minors Dominican Republic Legal Ecuador Legal El Salvador Legal Eritrea Illegal Grandparent—grandchild or parent—child Brother or half brother, sister or half-sister Same-sex relations are always prohibited From one to three years in prison Estonia Illegal (only incest between parent and child or grandparent and grandchild is illegal, incest between siblings is legal) Grandparent—grandchild or parent—childFrom two to eight years in prison Eswatini Illegal Offspring, sibling, parent or grandparent 25 years, if aged 14 years or less 20 years, if aged 14–18 years 10 years and E50.000, if 18 years or more 4 years and E20.000, if 18 years or more with consent Ethiopia Illegal Blood relatives whose marriage is prohibited by respective law Same-sex relations are always prohibited From three months to three years in prison Federated States of Micronesia Legal (1 state: Kosrae) / Illegal (3 states: Yap, Pohnpei and Chuuk)UN Report. Criminal codes: Yap, Chuuk, Pohnpei. Burden of proof of the relationship rests with the prosecution. Up to three years in prison (in Pohnpei and Yap) Up to three months in prison (in Chuuk) Fiji Illegal"Carnal knowledge of" (sexual intercourse with) parent, grandparent or sibling.Imprisonment for 20 years. France Legal Gabon Legal Georgia Illegal Lineal ancestors and descendants Full and half-siblings Up to two years in prison Germany Illegal (Penile-vaginal intercourse)/ Legal (other practices) Lineal ancestors and descendants with Penile-vaginal intercourse Full and half-siblings with Penile-vaginal intercourse Up to three years in prison or fine(descendants and siblings under 18 are not punished) Ghana Illegal Lineal ancestors and descendants Full and half-siblings Prison sentence Greece Illegal Lineal ancestors and descendants Full and half-siblings Uncle or aunt (by blood) Nephew or niece More than 10 years in prison for the ascending relative if the descending relative is 14 years old or younger, imprisonment if 15 to 17 years old, and up to two years in prison if 18 years and older Up to two years in prison if siblings or half-siblings or for the descending relative Grenada Illegal Daughter/son, granddaughter/grandson, sister/brother, aunt/uncle (by blood) or niece/nephew Guatemala Legal Guinea-Bissau Legal Guyana Legal (for opposite-sex couples) / Illegal (for same-sex couples) Same sex couples Life imprisonment Haiti Legal Honduras Legal Hong Kong Legal (for same-sex couples) / Illegal (for opposite-sex couples) Granddaughter, daughter, sister or mother (male) Grandfather, father, brother or son (female) Life imprisonment if aged 12 or younger 20 years imprisonment if aged 13 to 15 14 years imprisonment if aged 16 or older Consent of the Secretary of Justice is required for a prosecution Hungary Illegal Lineal ancestors and descendants Sibling Imprisonment not exceeding three years (for relatives in direct line) imprisonment not exceeding two years (for siblings) Iceland Illegal Lineal ancestors and descendants Full and half-siblings Up to eight years in prison for ascending relative Up to 12 years if descending relative is between 15 and 17 years old Up to four years in prison for siblings India LegalWhile there is no specific law in India that criminalizes consensual sexual relationships between adult relatives (hence technically considered "legal"), such relationships are heavily taboo and prohibited under most personal and marriage laws, such as the Hindu Marriage Act, 1955, which forbids unions within degrees of "sapinda" relationship unless custom permits. In some cases, courts have intervened based on public morality concerns, and other laws (e.g., the Protection of Children from Sexual Offences Act or Sections 376 and 354 of the IPC) apply where coercion, abuse, or minors are involved. Indonesia Illegal Lineal ancestors and descendants Full and half-siblings Uncle or aunt (by blood) (unless government permission explicitly required) Nephew or niece (unless government permission explicitly required) Grandaunt (by blood), granduncle (by blood), grandniece, grandnephew (unless government permission explicitly required) Up to 10 years in prison Ireland Legal (same-sex couples) / Illegal (opposite-sex couples) Granddaughter, daughter, mother, sister or half-sister (male) Grandfather, father, son, brother or half-brother (female) Up to 10 years in prison (male and female) Iran Illegal Lineal ancestors and descendants