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First-degree relative

The "degree of relationship" describes the proportion of genes shared by two blood relatives. A person's first degree relative is a parent, sibling,  or child. A first degree relative shares about half of their genes with the person.

A second degree relative of a person is an uncle, aunt, nephew, niece, grandparent, grandchild or half- sibling.  A second degree relative shares about one quarter of their genes with the person.

A third degree relative of a person is a first cousin, great-grandparent or great-grandchild.  A third degree relative shares about one eighth of their genes with the person.