CFR /  Title 12  /  Part 161  /  Sec. 161.24 Immediate family.

The term immediate family of any natural person means the following (whether by the full or half blood or by adoption):

(a) Such person's spouse, father, mother, children, brothers, sisters, and grandchildren;

(b) The father, mother, brothers, and sisters of such person's spouse; and

(c) The spouse of a child, brother, or sister of such person.