degree of kinship
degree of relationship between two people with a common ancester
second-degree relative
someone who shares 25% of a person's genes: uncles, aunts, nephews, nieces, grandparents, grandchildren, half-siblings, and double cousins
third-degree relative
blood relative that constitutes a segment of the extended family, sharing (on average) ⅛ (12.5%) of genes: first cousins, great grandparents, great grandchildren, etc.
first-degree relative
one's offspring, sibling or parent
fourth-degree relative
kinship relation sharing, on average, 1/16 of genes