A cousin in English kinship terminology is a relative with whom one shares a common grandparent or more distant ancestor, and who is not in one's own line of descent.

The term cousin never applies where there are other specific terms to describe relationships. These specific terms involve one's ancestors (mother, father, and all forms of grandparent) and their siblings (all forms of aunt and uncle), one's own descendants (child, grandchild, etc.), and one's own siblings (brother, sister) and their descendants (all forms of niece and nephew).

A system of degrees and removes is used to describe the relationship between the two cousins and the ancestor they have in common. The degree (first, second, third cousin, etc.) indicates the minimum number of generations separating either of the cousins from the common ancestor; the remove (once removed, twice removed, etc.) indicates the number of generations, if any, separating the two cousins from each other.

In this system, the child of one's aunt or uncle is one's first cousin. The child of one's first cousin is one's first cousin once removed.

The system can handle kinships going back many generations. In 2004, genealogists discovered that U.S. Presidential candidates George W. Bush and John Kerry shared a common ancestral couple in the 1500s. It was reported that the two men are sixteenth cousins, three times removed. [1] [2]

Non-genealogical usage often eliminates the degrees and removes, and refers to people with common ancestors merely as cousins or distant cousins.