Family member
Family member means, with respect to an individual:
(1) A dependent (as such term is defined in 45 CFR 144.103), of the individual; or
(2) Any other person who is a first-degree, second-degree, third-degree, or fourth-degree relative of the individual or of a dependent of the individual. Relatives by affinity (such as by marriage or adoption) are treated the same as relatives by consanguinity (that is, relatives who share a common biological ancestor). In determining the degree of the relationship, relatives by less than full consanguinity (such as half-siblings, who share only one parent) are treated the same as relatives by full consanguinity (such as siblings who share both parents).
(i) First-degree relatives include parents, spouses, siblings, and children.
(ii) Second-degree relatives include grandparents, grandchildren, aunts, uncles, nephews, and nieces.
(iii) Third-degree relatives include great-grandparents, great-grandchildren, great aunts, great uncles, and first cousins.
(iv) Fourth-degree relatives include great-great grandparents, great-great grandchildren, and children of first cousins.
Source
45 CFR § 160.103
Scoping language
Except as otherwise provided, the following definitions apply to this subchapter: