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A cousin is a relative with whom a person shares one or more common ancestor(s) (other than a parent, child/descendant, sibling, child/descendant of a sibling, or sibling of a parent/ancestor). However in common parlance, "cousin" normally specifically means "first cousin".

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 more precisely specify kinships with common ancestors existing any number of generations in the past, though common usage often eliminates the degrees and removals and refers to people with common ancestry as simply "distant cousins" or "relatives".

Basic definitions [edit]

The ordinals in the terms "first cousins", "second cousins", "third cousins", describe the "degree" of the cousin relationship. The degree of two cousins' relationship is determined by the number of generations to their closest common ancestor.^[1] When the cousins are not the same generation, they are described as "removed". In this case, the smaller number of generations to the common ancestor is used to determine the degree, and the difference in generations determines the number of times removed. Note that the ages of the cousins are irrelevant to the definition of the cousin relationship.

Additional terms [edit]

The following is a list of less common cousin terms.

Kissing cousins are defined by the Oxford English Dictionary as "relatives or friends with whom one is on close enough terms to greet with a kiss".^[3]

Relationship charts [edit]

Cousin chart [edit]

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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 [edit]

Canon Law Relationship Chart. See an example of how to use chart.

Another visual chart used in determining the legal relationship between two people who share a common ancestor is based upon a diamond 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 are descended) in the top space in the diamond-shaped chart, and then following each line down the outside edge of the chart. Upon reaching the final place along the opposing outside edge for each person, the relationship is then determined by following that line inward to the point where the lines intersect. 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 parents are 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, the two would meet in the "brother/sister" 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.

Mathematical definitions [edit]

There is a mathematical way to identify the degree of cousinship shared by two individuals. In the description of each individual's relationship to the most recent common ancestor, each "great" or "grand" has a numerical value of 1. The following examples demonstrate how this is applied.

Example: If person one's great-great-great-grandfather is person two's grandfather, then person one's "number" is 4 (great + great + great + grand = 4) and person two's "number" is 1 (grand = 1). The smaller of the two numbers is the degree of cousinship. The two people in this example are first cousins. The difference between the two people's "numbers" is the degree of removal. In this case, the two people are thrice (4 − 1 = 3) removed, making them first cousins three times removed.

Example 2: If someone's great-great-great-grandparent (great + great + great + grand = 4) is another person's great-great-great-grandparent (great + great + great + grand = 4), then the two people are 4th cousins. There is no degree of removal, because they are on the same generational level (4 − 4 = 0).

Example 3: If one person's great-grandparent (great + grand = 2) is a second person's great-great-great-great-great-grandparent (great + great + great + great + great + grand = 6), then the two are second cousins four times removed. The first person's "number" (2) is the lower, making them second cousins. The difference between the two numbers is 4 (6 − 2 = 4), which is the degree of removal (generational difference).

Alternative definitions [edit]

Asymmetric definitions [edit]

The definitions discussed in the article above are the ones found in dictionaries of standard English, but they are not universal. At least one alternative usage also exists.

In this alternative system, the degree of the relationship from cousin A to cousin B is determined by the distance from A to the common ancestor and the number of times removed is the difference in generations between A to B. Sometimes "upwards" or "downwards" is used to indicate the direction of this difference. For example, if A has a grandparent whose sibling is B's parent, then B is A's "first cousin, once removed (upwards)", whereas A is B's "first cousin once removed (downwards)".^[4] Note that this is not standard terminology, and is completely absent from many major dictionaries.^[5]

As seen in this example, this usage is asymmetric, since different terms are used to represent A's relationship to B and B's relationship to A. By contrast, the standard usage of "cousin" discussed in the main part of this article is symmetric (in this example, the standard terminology would be that A is B's first cousin once removed, and B is A's first cousin once removed), and is also dyadic (for example, one can say "A and B are first cousins once removed").^[6]

Colloquial usage [edit]

In day to day speech, "cousin" is often used unmodified. Normally it means a first cousin, but some people use the term "cousin" to refer to cousins of all types, such as first, second, and third cousins, as well as cousins once or more times removed. Modifier terms such as "half-cousin" or "step-cousin" are rarely used in everyday speech.^{[citation needed]}

Usage for extremely distant relations [edit]

Although use of the word "cousin" in this context is infrequent (especially outside of evolutionary literature), any two individual organisms regardless of their respective species (or any other level of taxonomy) are in fact very distant cousins by virtue of shared descent from a single cell whose descendants survived beyond the Paleoarchean Era.^[7][8]

See also [edit]

• Collateral descendant
• Consanguinity
• Cousin marriage
• Cross cousin
• Family
• Genealogical numbering systems
• Generation
• Kinship terminology
• List of coupled cousins
• Most recent common ancestor
• Parallel cousin

References [edit]

External links [edit]

Look up cousin in Wiktionary, the free dictionary.

• Genealogy.com definition of various cousins
• Genealogy.com: What makes a cousin?
• Genetic Genealogy