Incest is defined as sexual relations between closely related persons (often within the immediate family) such that it is either illegal or socially taboo. The type of sexual activity and the nature of the relationship between persons that constitutes a breach of law or social taboo varies by culture and by jurisdiction.

The majority of incest cases reported in scientific studies are between adults and prepubescent or adolescent children, and particularly between fathers or other male relatives, and girls. This is a form of child sexual abuse that has been shown to be one or the most extreme forms of childhood trauma, a trauma which often does serious and long-term psychological damage, especially in the case of parental incest.

Adults who were incestuously victimized by adults in their childhood often suffer from low self-esteem, difficulties in interpersonal relationships, and sexual dysfunction; and are at an extremely high risk of many mental disorders including depression, anxiety, phobic avoidance reactions, somatoform disorder, substance abuse, borderline personality disorder, and complex post-traumatic stress disorder.

Consensual mutually-desired adult incest is very rare, found almost exclusively where kin were separated early in life and therefore did not experience early association and the related development of the natural adaptation for incest avoidance. Consensual incest between adults is criminalized in most countries, although it is seen by some as a victimless crime.

Incest can refer to sexual activity between family members of either gender, and can include family members of any age, and can be either consensual or non-consensual (depending on local laws, particularly age of consent). However, which family members constitute those covered by the incest prohibition is determined by the society in which the persons live. Some societies consider it to include only those who live in the same household, or who belong to the same clan or lineage; other societies consider it to include "blood relatives;" other societies further include those related by adoption or marriage as well.

Most societies have some form of incest avoidance. The incest taboo is one of the most common of all cultural taboos, both in current nations and many past societies, with legal penalties imposed in some places. Most modern societies have legal or social restrictions on closely consanguineous marriages. However, in some societies, like Ancient Egypt, brother-sister, father-daughter and mother-son relations were practiced among royalty. In addition, the Balinese and some Inuit tribes have altogether different beliefs of what constitutes illegal and immoral incest.


Between adults and children

Incest perpetrated by an adult of either gender against a child is called " intrafamilial child sexual abuse". The most-often reported form of incest is of this inherently abusive form. Father-daughter and stepfather-daughter incest is most commonly reported, with most of the remaining reports consisting of mother/stepmother-daughter/son incest. Father-son incest is reported less often, however it is not known if the prevalence is less, because it is under-reported by a greater margin. Prevalence of parental child sexual abuse is difficult to assess due to secrecy and privacy; some estimates show 20 million Americans have been victimized by parental incest as children.

According to the National Center for Victims of Crime a large proportion of rape committed in the United States is perpetrated by a family member:

Emotional incest occurs when a parent relates to a child as a substitute for an adult partner. That child may become emotionally bonded to, and codependent with, the parent. Emotional incest usually occurs before physical parent-child incest. Even without physical sexual contact, the consequences to such "bonded" children include a lifetime of partnership difficulties, according to Martyn Carruthers who wrote that this is a socially accepted form of child abuse in many countries.

The ISNA reported that a counselling hotline stated that a large percentage of the calls they handle deal with the issue of parental child abuse.

The Goler clan is a specific instance in which child sexual abuse in the form of forced adult/child and sibling/sibling incest took place over at least three generations. A number of Goler children were victims of sexual abuse at the hands of fathers, mothers, uncles, aunts, sisters, brothers, cousins, and each other. During interrogation by police, several of the adults openly admitted to engaging in many forms of sexual activity, up to and including full intercourse, multiple times with the children. Sixteen adults (both men and women) were charged with hundreds of allegations of incest and sexual abuse of children as young as five.

Between childhood siblings

Many types of sexual contact between children (e.g., "playing doctor") are not considered harmful or abnormal, but become child-on-child sexual abuse when there is lack of consent, coercion, or simply an imbalance of power or knowledge in the relationship. Childhood sibling-sibling incest is also considered to be widespread but rarely reported. The most commonly reported form of abusive sibling incest is abuse between an older brother and a younger brother or sister.

According to a study by Floyd Martinson, 10-15% of college students reported childhood sexual experiences with a brother or sister, mostly fondling of genitals rather than sexual intercourse. Of those, 30% reported negative reactions and 30% reported positive reactions; 25% of the reported experiences involved coercion and there was a correlation of coercion with the negative responses. A 2006 study showed a large portion of adults who experienced sibling incest have distorted or disturbed beliefs both about their own experience and the subject of sexual abuse in general. An observational study in 1993 found that 16 percent of the 930 adult women interviewed reported that they had been sexually abused by a sibling before they were 18 years old.

Sibling incest is most prevalent in families where one or both parents are often absent or emotionally unavailable, with the abusive siblings using incest as a way to assert their power over a weaker sibling and thereby express their feelings of hurt and rage. Absence of the father in particular has been found to be a significant element of most cases of sexual abuse of female children by a brother. The damaging effects on both childhood development and adult symptoms resulting from brother-sister sexual abuse are similar to the effects of father-daughter, including substance abuse, depression, suicidality, and eating disorders.

Between consenting adults

Incest between consenting adults is sexual behavior between adult, blood relatives (which can include parents and adult offspring, siblings, cousins, etc.) that is not coerced or forced in any way. While incest between consenting adults has not been widely reported in the past, the internet has shown that this behavior does take place, possibly more often than many people realize. Internet chatrooms and topical websites exist that provide support for incestuous couples.

Proponents of incest between consenting adults draw clear boundaries between the behavior of consenting adults and rape, pedophilia, and abuse. According to one incest participant who was interviewed for an article in The Guardian

In Slate Magazine, William Saletan drew a legal connection between gay sex and incest between consenting adults. As he described in his article, in 2003, U.S. Senator Rick Santorum publicly derided the theory of the Supreme Court ruling to allow private consensual sex in the home (primarily as a gay rights move). He stated: "If the Supreme Court says that you have the right to consensual sex within your home, then you have the right to bigamy, you have the right to polygamy, you have the right to incest, you have the right to adultery." However, David Smith of the Human Rights Campaign professed outrage that Santorum placed being gay on the same moral and legal level as someone engaging in incest. Saletan argued that, legally and morally, there is essentially no difference between the two, and went on to support incest between consenting adults being covered by a legal right to privacy.

Between adult siblings
The most public case of consensual adult sibling incest in recent years is the case of a couple from Leipzig, Germany. The couple became intimately close after the death of their mother and in 2001, had their first child together (they have a total of four). The public nature of their relationship, and the repeated prosecutions and even jail time they have served as a result, has caused some in Germany to question whether incest between consenting adults should be punished at all. For all intents and purposes, the couple are happy together and incest between consenting adults in general, as described in a Der Spiegel article about them, is a victimless crime.

Between adult cousins

Many cultures consider relationships between parallel cousins incestuous, but not those between cross cousins, although the degree of genetic relationship does not differ. In some Muslim countries, intimate relationships between cousins are not considered incest provided that they are married.

Incest defined through marriage
Some cultures include relatives by marriage in incest prohibitions; these relationships are called affinity rather than consanguinity. For example, the question of the legality and morality of a widower who wished to marry his deceased wife's sister was the subject of long and fierce debate in the United Kingdom in the 19th century, involving, among others, Matthew Boulton. In medieval Europe, standing as a godparent to a child also created a bond of affinity.



The word 'incest' was introduced into Middle English around 1225 as a legal term to describe the crime of familial incest as we know it today. It was also used to describe sexual relations between married persons, one of whom had taken a vow of celibacy (often called spiritual incest). It derives from the Latin incestus or incestum, the substantive use of the adjective incestus meaning 'unchaste, impure', which itself is derived from the Latin castus meaning 'chaste'. The derived adjective incestuous does not appear until the 16th century.

Prior to the introduction of the Latin term, incest was known in Old English as sibbleger (from sibb 'kinship' + leger 'to lie') or m??h?med (from m?? 'kin, parent' + h?med 'sexual intercourse') but in time, both words fell out of use.

Ancient civilizations

It is relatively accepted that incestuous marriages were widespread at least during the Graeco-Roman period of Egyptian history. Numerous papyri and the Roman census declarations attest to many husbands and wives being brother and sister (Lewis, 1983; Bagnall and Frier, 1994; Shaw, 1993). In Hopkins (1980) this is conclusively demonstrated, and more recent scholars in the field have not questioned it. Some of these incestuous relationships were in the royal family, especially the Ptolemies (see the biography of Cleopatra, who married more than one of her brothers).

The fable of Oedipus, with a theme of inadvertent incest between a mother and son, ends in disaster and shows ancient taboos against incest as Oedipus is punished for incestuous actions by blinding himself.

Incestuous unions were frowned upon and considered as nefas (against the laws of gods and man) in Roman times, and were explicitly forbidden by an imperial edict in AD 295, which divided the concept of incestus into two categories of unequal gravity: the incestus iuris gentium, which was applied to both Romans and non-Romans in the Empire, and the incestus iuris civilis, which concerned only Roman citizens. Therefore, for example, an Egyptian could marry an aunt, but a Roman could not. Despite the act of incest being unacceptable within the Roman Empire, Roman Emperor Caligula is rumored to have had open sexual relationships with all three of his sisters, (Julia Livilla, Drusilla, and Agrippina the Younger). The taboo against incest in Ancient Rome is demonstrated by the fact that politicians would use charges of incest (often false charges) as insults and means of political disenfranchisement.

Hypothesis of incest avoidance origins

Some researchers hypothesize that humans have a kin recognition ability that functions in part to enable incest avoidance between close relatives, thereby protecting the gene pool of the family or tribe from excessive damage by inbreeding; and, that this kin recognition system may form a biological basis for social and psychological prohibitions against incest. Lieberman et al. (2003) found that childhood co-residency with an opposite-sex sibling (biologically related or not) was significantly correlated with moral repugnance toward third-party sibling incest.

Laws regarding incest

Incest is illegal in many jurisdictions. The exact legal definition of "incest," including the nature of the relationship between persons, and the types sexual activity, varies by country, and by even individual states or provinces within a country. These laws can also extend to marriage between said individuals.

Religious views on incest


In the story of Sodom and Gomorrah in the Book of Genesis in the Bible, Lot's two daughters have sex with him to carry on their lineage.

Later, the Book of Leviticus lists prohibitions against sexual relations between various pairs of family members. Men are prohibited, on pain of death, to have sexual relations with their daughters, mothers, aunts, and various other relations. (Father-daughter incest is covered by a prohibition on sexual relationships between a man and any daughter born to any woman he has had sexual relationships with, thereby prohibiting his incest not only with his own daughters but also with women who could be his stepdaughters by marriage.)

It is to be noted that the Book of Leviticus, says nothing about the marriage of cousins, see Cousin couple.


The Quran mentions incest which prohibits a man from having sexual relationships with his mother, daughter, sister, paternal aunt, maternal aunt or niece. However, Islam allows for marriage with cousins and other more distant relatives. Only in case of marriage does Islam allow sexual relations between cousins and other distant relatives.


Hinduism speaks of incest in highly abhorrent terms. Hindus were greatly fearful of the bad effects of incest and thus practice to date strict rules of both endogamy and exogamy, that is, marriage in the same caste (varna) but not in the same family tree (gotra) or bloodline (Parivara). Marriages within the gotra ("swagotra" marriages) are banned under the rule of exogamy in the traditional matrimonial system. People within the gotra are regarded as kin and marrying such a person would be thought of as incest.

In some South Indian communities, where gotra membership passed from father to children, marriages were allowed between uncle and niece, while such marriages were forbidden in matrilineal communities, like Malayalis and Tuluvas, where gotra membership was passed down from the mother. A much more common characteristic of south Indian Hindu society is permission of marriage between cross-cousins (children of brother and sister). Thus, a man is allowed to marry his maternal uncle's daughter or his paternal aunt's daughter but is not allowed to marry his paternal uncle's daughter, a parallel cousin, who is treated as a sister.

North Indian Hindu society not only follows rules of gotra for marriages, but also has many regulations which go beyond the basic definition of gotra which result in few occurrences of similarly incestuous relationships.


Asian societies shaped by Buddhist traditions takes a strong ethical stand in human affairs and sexual behavior in particular. In most of those societies, incest is regarded as highly abhorrent. However, unlike most other world religions, most variations of Buddhism, does not go in to details what is right and what is wrong in mundane activities of life. Incest (or any other detail of human sexual conduct for that matter) is not specifically mentioned in any of the religious scriptures. The most common formulation of Buddhist ethics are the Five Precepts and the Eightfold Path, one should neither be attached to nor crave sensual pleasure. These precepts take the form of voluntary, personal undertakings, not divine mandate or instruction. The third of the Five Precepts is "To refrain from committing sexual misconduct". It is understandable that incest itself could constitute "sexual misconduct".. 'Sexual misconduct' is a loose term, and is subjected to interpretation relative to the social norms of the followers. In fact, Buddhism in its fundamental form, does not define what is right and what is wrong in absolute terms for lay followers. Therefore the interpretation of whether incest for a layperson is right or wrong, is not a religious matter as far as Buddhism is concerned.

See also


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