Cousin-in-law

A cousin is a relative with whom a person shares one or more common ancestors. In the general sense, cousins are two or more generations away from any common ancestor, thus distinguishing a cousin from an ancestor, descendant, sibling, aunt, uncle, niece, or nephew. However in common parlance "cousins" typically refers to "first cousins", individuals who share a grandparent.

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 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".

People are related with a type of cousin relationship if they share a common ancestor and the most recent common ancestor is more than two generations apart for both parties. This means neither person is an ancestor of the other (descendants and ancestors), they do not share a parent (siblings), and neither is a sibling of a common ancestor (aunts/uncles and nephews/nieces).

The cousin relationship is further segmented 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 number of generations the cousins have to go back before finding the same most recent common ancestor is different, the cousin relationship is said to be removed. The difference between the number of generations is the removal. For example if one person's grandfather is the other person's great-grandfather or one person's great-grandfather is the other person's great-great-grandfather the cousins are 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 first cousins have to go one generation beyond the parents (the grandparents) before finding a common ancestor, if they had to go back two generations beyond the parents (great grandparents) they would be second cousins.

A person shares a first cousin or cousin relationship with the children of their parents siblings. Cousins share least one set of grandparents. In the example to the right Joseph and Julie are first cousins.

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Wikipedia