Cousin

For other uses, see Cousin (disambiguation).

In kinship terminology, a cousin is a relative with whom a person shares one or more common ancestors. The term is rarely used when referring to a relative in an immediate family in which there is a more specific term (e.g., mother, father, sister, brother, etc.). The term "blood relative" can be used synonymously and establishes the existence of a genetic link. Systems of "degrees" and "removals" are used in the English speaking world to describe the relationship between two cousins and the ancestor they have in common. Various governmental entities have established systems for legal use that can handle 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 "cousins" or "distant cousin".

By extension, the term "cousin" can also be used when referring to the genetic relationships between humans and any other form of life, as per the theory of evolution of all life on Earth descending from one common ancestor. However the term in this sense is most commonly restricted to the fields of study surrounding ecological genetics.

Basic Cousin Definitions

First cousins, second cousins, third cousins, etc, are of the same generation regardless of age. Cousins who are one or more times "removed" are of of different generations, regardless of age, from the closest common generation relationship.

Term	Definition	Example
First Cousins	The children of two siblings and their respective spouses.	Bill and Sally are first cousins because their fathers were brothers.
Second Cousins	The children of two first cousins and their respective spouses.	Bob and Sarah are second cousins because Bob's father, Bill, and Sarah's mother, Sally, are first cousins
Third Cousins	The children of two second cousins and their respective spouses.	Brian and Stephanie are third cousins because Brian's father, Bill, and Stephanie's mother, Sarah, are second cousins.
First Cousin Once Removed	Two people for whom a first cousin relationship is one generation removed for one of them.	Bob and his fathers's first cousin, Sally, are first cousins once removed to each other. They are one generation removed from the common generational relationship between Bob's Father (Bill) and Sally.
First Cousin Twice Removed	Two people for whom a first cousin relationship is two generations removed for one of them.	Brian and his grandfather's first cousin, Sally, are first cousins twice removed. They are two generations removed from the common generational relationship between Brian's grandfather (Bill), and Sally.
Second Cousin Once Removed	Two people for whom a second cousin relationship is one generation removed for one of them.	Brian and his father's second cousin, Sarah, are second cousins once removed. They are one generation removed from the common second cousin relationship between Brian's father (Bob) and Sarah.

Additional Cousin Terms

The following is a list of less common cousin terms.

Term	Definition
Double Cousins	Double first cousins arise when two siblings of one family reproduce with two siblings of another family. The resulting children are related to each other through both parents' families. Double first cousins share both sets of grandparents in common and have double the degree of consanguinity of ordinary first cousins. Children of double first cousins are double second cousins to each other.
Half-Cousin	Half-cousins are the children of two half-siblings and their respective partners e.g., The children of two half-brothers and their wives.
Step-Cousin	Step-cousins are either stepchildren of an individual's aunt or uncle, or children of one's step-aunt or uncle.
Cousin-In-Law	A cousin-in-law is the spouse of an individual's cousin, or the cousin of one's spouse.
Maternal/Paternal Cousin	A term that specifies whether the individual is one's cousin on the mother's side (maternal) or father's side (paternal).

Colloquial Usage

Although precise legal nomenclature exists, in day to day speech, "cousin" is often used unmodified. Thus a person may use the term "cousin" to refer to cousins of all types, e.g. 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. The term "cousin" is also sometimes used for people someone is close to, even if they are not actually blood relatives.

Charts of Cousin Relationships

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.

Additional modifying words are used to clarify the exact degree of relatedness between the two people. Ordinal numbers are used to specify the number of generations between individuals and a common ancestor, and further clarification of exact cousinship is made by specifying the difference in generational level between the two cousins, if any, by using degrees of removal. For example, "first cousins once removed" describes two individuals with the common ancestor being the grandparent of one cousin (one "degree") and the great-grandparent of the other cousin (two "degrees"). The degree of lowest number is considered the degree. The cousins themselves are one generation apart from each other (one "remove"). So, the difference between the degrees is the "removed" part of the equation in this example.

If one person's →		Grandparent	Great-grandparent	Great-great-grandparent	Great-great-great-grandparent	Great-great-great-great-grandparent	Great-great-great-great-great-grandparent
is the other person's ↓	then they are ↘
Grandparent		1st cousins	1st cousins once removed	1st cousins twice removed	1st cousins thrice removed	1st cousins four times removed	1st cousins five times removed
Great-grandparent		1st cousins once removed	2nd cousins	2nd cousins once removed	2nd cousins twice removed	2nd cousins thrice removed	2nd cousins four times removed
Great-great-grandparent		1st cousins twice removed	2nd cousins once removed	3rd cousins	3rd cousins once removed	3rd cousins twice removed	3rd cousins thrice removed
Great-great-great-grandparent		1st cousins thrice removed	2nd cousins twice removed	3rd cousins once removed	4th cousins	4th cousins once removed	4th cousins twice removed
Great-great-great-great-grandparent		1st cousins four times removed	2nd cousins thrice removed	3rd cousins twice removed	4th cousins once removed	5th cousins	5th cousins once removed
Great-great-great-great-great-grandparent		1st cousins five times removed	2nd cousins four times removed	3rd cousins thrice removed	4th cousins twice removed	5th cousins once removed	6th cousins

Canon Law Relationship Chart

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 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

There is a mathematical way to identify the degree of cousinship shared by two individuals. Each "great" or "grand" in the description of one individual's relationship to the common ancestor has a numerical value of 1.

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 thrice 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).

See also

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

External links

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