Commonly "cousin" refers to a "first cousin" or equivalently "full cousin". First cousins are people whose most recent common ancestor is a grandparent. This relationship was also called cousin-german in the past.
More generally, cousin is a type of familial relationship in which people with a known common ancestor are both two or more generations away from their most recent common ancestor. This distinguishes a cousin from an ancestor, descendant, sibling, aunt, uncle, niece, or nephew.
Systems of "degrees" and "removals" are used in the English-speaking world to describe the exact relationship between two cousins (in the broad sense) and the ancestor they have in common. Various governmental entities have established systems for legal use that can precisely specify kinship with common ancestors any number of generations in the past. Common usage often eliminates the degrees and removals, and refers to people with common ancestry as simply "distant cousins" or "relatives".
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Basic definitions
People are related with a type of cousin relationship if they share a common ancestor and the most recent common ancestor is two or more generations away from both people. This means neither person is an ancestor of the other, they do not share a parent (siblings), and neither is a sibling of a common ancestor (aunts/uncles and nieces/nephews).
The cousin relationship is further detailed by degree and removal. For example the second cousin once removed relationship is a second-degree cousin with one removal.
The removal of the cousin relationship is the number of generations the cousins are apart. When the cousins are separated by a different number of generations from the most recent common ancestor, the cousin relationship is removed. The difference between the number of generations for each cousin is the removal. For example if the most recent common ancestor is 2 generations prior for one person and 3 generations prior for the other (one person's grandfather is the other person's great-grandfather) or the most recent common ancestor is 3 generations prior for one person and 4 generations prior for the other (one person's great-grandfather is the other person's great-great-grandfather) the cousins are separated by one generation and therefore once removed. Note that two people can be removed but be around the same age due to differences in birth dates of parents children and other relevant ancestors.
The degree of the cousin relationship is the number of generations prior to the parents before a most recent common ancestor is found. If the cousins are removed, the smaller number of generations to the most recent common ancestor is used to determine the degree of the cousin relationship. For example if one of the cousins has to go back one generation beyond their parents (the grandparents) before finding the most recent common ancestor and the other has to go back one or more they are first cousins. If one had to go back two generations beyond the parents (great grandparents) and the other had to go back two or more they would be second cousins.
Examples
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Relationship charts
Cousin chart
A "cousin chart", or "table of consanguinity", is helpful in identifying the degree of cousin relationship between two people using their most recent common ancestor as the reference point. Cousinship between two people can be specifically described in degrees and removals by determining how close, generationally, the common ancestor is to each person.
Canon law relationship chart
Another visual chart used in determining the legal relationship between two people who share a common ancestor is based upon a rhombus shape, usually referred to as a "canon law relationship chart".
The chart is used by placing the "common progenitor" (the most recent person from whom both people (A and B) are descended) in the top space in the diamond-shaped chart, and assigning a direction (arbitrarily, left or right) to each of the two people, A and B. Then follow the line down the outside edge of the chart for each of the two people until their respective relationship to the common ancestor is reached. Upon determining that place along the opposing outside edge for each person, their relationship is then determined by following the lines inward to the point of intersection. The information contained in the common "intersection" defines the relationship.
For a simple example, in the illustration to the right, if two siblings use the chart to determine their relationship, their common parent (either one, if there are two) is placed in the topmost position, and each child is assigned the space below and along the outside of the chart. Then, following the spaces inward, they would intersect in the "brother" diamond. If their children want to determine their relationship, they would follow the path established by their parents but descend an additional step below along the outside of the chart (showing that they are grandchildren of the common progenitor); following their respective lines inward, they would come to rest in the space marked "1st cousin". In cases where one side descends the outside of the diamond further than the other side because of additional generations removed from the common progenitor, following the lines inward shows both the cousin rank (1st cousin, 2nd cousin) plus the number of times (generations) "removed".
In the example provided at the right, generations one (child) through ten (8th great-grandchild) from the common progenitor are provided; however, the format of the chart can easily be expanded to accommodate any number of generations needed to resolve the question of relationship.
Cousin marriage
Cousin marriage is important in several anthropological theories which often differentiate between matriarchal and patriarchal parallel and cross cousins. A parallel cousin is a cousin from a parent's same-sex sibling, while a cross cousin is from a parent's opposite-sex sibling.
Currently about 10% and historically as high as 80% of all marriages are between first or second cousins. Cousin marriages are often arranged. Anthropologists believe it is 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 over half of all marriages are between first and second cousins. Some of the countries in this region this may exceed 70%. Just outside this region it is often legal but infrequent. In other places it is legally prohibited and culturaly equlivelent to incest Supporters of cousin marriage often view the prohibition as discrimination, while opponents cite the potential immorality.
Married couples that possess higher than normal consanguinity, shared identical DNA and genetic material, have an increased chance of sharing genes for recessive traits. The percentage of consanguinity between any two individuals decreases fourfold as the most recent common ancestor recedes one generation. First cousins have four times the consanguinity of second cousins, while first cousins once removed have half that of first cousins. Double first cousins have twice that of first cousins and are as related as half-siblings. Children of these marriages may have an increased risk of genetic disorders, particularly if their parents both carry a harmful recessive mutation.
Additional terms
The following is a list of less common cousin terms.
Source of the article : Wikipedia
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