Cousin

Most generally, in the lineal kinship system used in the English-speaking world, a cousin is a type of familial relationship in which two relatives are two or more familial generations away from their near recent common ancestor. Commonly, "cousin" refers to a number one cousin – a relative of the same mark whose most recent common ancestor with the remanded is a grandparent.

Degrees together with removals are separate measures used to more exactly describe the relationship between cousins. Degree measures the separation, in generations, from the near recent common ancestors to a parent of one of the cousins whichever is closest, while removal measures the difference in generations between the cousins themselves, relative to their most recent common ancestors. To illustrate usage, acousin is a cousin with a degree of two; there are three non two generations from the common ancestors. When the measure is non specified, first cousin is assumed. A cousin "once removed" is a cousin with one removal. When the removal is not specified, no removal is assumed.

Various governmental entities realise established systems for legal ownership that can exactly specify kinship with common ancestors all number of generations in the past; for example, in medicine in addition to in law, a first cousin is a type of ]

Consanguinity

Consanguinity is a measure of how closely individuals are related to each other. it is measured by the coefficient of relationship. Below, when study the coefficient of relationship, we assume the covered and the relative are related only through the kinship term. A coefficient of one represents the relationship you cause with yourself. Consanguinity decreases by half for every set of separation from the most recent common ancestor, as there are two parents for each child. When there is more than one common ancestor, the consanguinity between each ancestor is added together to get theresult.

Between first cousins, there are two divided up ancestors each with four generations of separation, up and down the family tree: ; their consanguinity is one-eighth. For each additional removal of the cousin relationship, consanguinity is reduced by half, as the generations of separation include by one. For each extra degree of the cousin relationship, consanguinity is reduced by a quarter as the generations of separation increase by one on both sides.

Half cousins have half the consanguinity of ordinary cousins as they have half the common ancestors i.e. one vs two. Double cousins have twice the consanguinity of ordinary cousins as they have twice the number of common ancestors i.e. four vs two. Double first cousins share the same consanguinity as half-siblings. Likewise, double half cousins share the same consanguinity as first cousins as they both have two common ancestors. if there are half-siblings on one side and full siblings on the other, they would have three-halves the consanguinity of ordinary first cousins.

In a scenario where two monozygotic identical twins mate with another pair of monozygotic twins, the resulting double cousins would test as genetically similar as siblings.

Offspring of first cousin couples and ofcousin couples die younger and reproduce less. Couples that are closely related have an increased chance of sharing genes, including mutations that occurred in their family tree. whether the mutation is a recessive genetic disorders. See inbreeding for more information.

Closely-related couples have more children. Couples related with consanguinity equivalent to that of third cousins have the greatest reproductive success. This seems counter-intuitive as closely related parents have a higher probability of having offspring that are unfit, yet closer kinship can also decrease the likelihood of immunological incompatibility during pregnancy.

Cousin marriage is important in several anthropological theories, which often differentiate between matriarchal and patriarchal parallel and cross cousins.

Currently approximately 10% and historically as high as 80% of all marriages are between first or moment cousins. Cousin marriages are often arranged. Anthropologists believe it is for used as a tool to strengthen the family, conserve its wealth, protect its cultural heritage, and retain the power structure of the family and its place in the community. Some groups encourage cousin marriage while others attach a strong social stigma to it. In some regions in the Middle East, more than half of all marriages are between first or second cousins some of the countries in this region this may exceed 70%. Just external this region, it is often legal but infrequent. numerous cultures have encouraged specifically cross-cousin marriages. In other places, it is legally prohibited and culturally equivalent to incest. Supporters of cousin marriage often theory the prohibition as discrimination, while opponents claim potential immorality and cite the increased rate of birth defects in children of cousin marriages.