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.
