Cousin

A cousin is a relative who is the child of an aunt or uncle, known specifically as a first cousin. In the English-speaking kinship system, a cousin relationship exists when two people share a common ancestor and are at least two generations removed from that ancestor—meaning they are not siblings, not parent and child, and not aunt/uncle or niece/nephew to each other. To describe these relationships more precisely, the system uses "degrees" and "removals." The degree (first cousin, second cousin, etc.) measures how far the relationship is from the most recent common ancestor, starting at one for first cousins and increasing with each generation. If the cousins are from different generations, "removal" indicates the generational gap; when no removal is mentioned, none is assumed. Because the single word "cousin" covers both degrees and removals, a person can have many more cousins among living relatives than any other type of family relationship. Genealogists can trace hundreds of cousin connections across centuries for some individuals.

Basic definitions: A cousin relationship requires that neither person is an ancestor of the other, they do not share a parent, and neither is the sibling of the other’s parent. The degree is the number of generations after the common ancestor before a parent of one cousin appears—essentially, the separation from the common ancestor minus one. If the cousins are not the same number of generations from the common ancestor, the cousin with the smaller separation determines the degree. The removal is the difference in generations between the two cousins. Two people can be removed yet be similar in age due to differences in birth dates of parents, children, or other ancestors.

Additional terms: A "full cousin" or "cousin-german" means a first cousin with no removals. "Cousin-uncle/aunt" and "cousin-niece/nephew" describe the direction of removal, sometimes used in Mennonite families—uncle/aunt refers to an older generation, niece/nephew to a younger one. Alternatively, "up" and "down" indicate direction; for example, George is a cousin-nephew of David, or a first cousin once removed down, while David is George’s cousin-uncle, or cousin once removed up. For more removals, "grand" or "great" are added, so David is a cousin-granduncle from Clara’s perspective (cousin twice removed up), and Clara is a cousin-grandniece (first cousin twice removed down). "Grandcousin" sometimes refers to the grandchild of a first cousin or the first cousin of a grandparent—a first cousin twice removed. "Kissing cousin" is a term for a distant relative familiar enough to greet with a kiss.

Gender-based distinctions: A maternal cousin is related through the mother’s side, and a paternal cousin through the father’s side; this relationship is not reciprocal, as one person’s maternal cousin may be the other’s paternal cousin. Parallel and cross cousins are reciprocal. Parallel cousins descend from same-sex siblings—both maternal or both paternal. Cross cousins descend from opposite-sex siblings; a cross first cousin exists when one person is a maternal cousin and the other a paternal cousin.

Multiplicities: Double cousins are related through two different branches, occurring when siblings from one family reproduce with siblings from another family. This results in children related through both parents, known as "cousins on both sides"; double first cousins share both sets of grandparents. Half cousins descend from half siblings and share one grandparent; children of two half siblings are first half cousins. If half siblings have children with another pair of half siblings, the children are double half first cousins, sharing one grandparent on each side. Though no standard term exists, cousins can share three grandparents if a pair of half siblings has children with a pair of full siblings—a real-world example is Baldwin V of Jerusalem and Maria of Montferrat.

Cousins-in-law and non-blood relations: Step-cousins are stepchildren of an individual’s aunt or uncle, nieces/nephews of a step-parent, or children of a parent’s step-sibling. A cousin-in-law is the cousin of one’s spouse, the spouse of one’s cousin, or the spouse of one’s spouse’s cousin.

Consanguinity: Consanguinity measures how closely individuals are related, using the coefficient of relationship.