Incest ( IN-sest) is sex between close relatives, for example a brother, sister, or parent. This typically includes any kind of sexual activity between people in consanguinity (blood relations), and sometimes those related by lineage. It is condemned and considered immoral in many societies. It can lead to an increased risk of genetic disorders in children in case of pregnancy from incestuous sex.
The incest taboo is one of the most widespread of all cultural taboos, both in present and in past societies. Most modern societies have laws regarding incest or social restrictions on closely consanguineous marriages. In societies where it is illegal, consensual adult incest is seen by some as a victimless crime. Some cultures extend the incest taboo to relatives with no consanguinity, such as milk-siblings, stepsiblings, and adoptive siblings, albeit sometimes with less intensity. Third-degree relatives (such as half-aunt, half-nephew, first cousin) on average have 12.5% common genetic heritage, and sexual relations between them are viewed differently in various cultures, from being discouraged to being socially acceptable. Children of incestuous relationships have been regarded as illegitimate, and are still so regarded in some societies today. In most cases, the parents did not have the option to marry to remove that status, as incestuous marriages were, and are, normally also prohibited.
