Title 5, §3110 of the United States Code states:
A public official may not appoint, employ, promote, advance, or advocate for appointment, employment, promotion, or advancement, in or to a civilian position in the agency in which he is serving or over which he exercises jurisdiction or control any individual who is a relative of the public official.
5 U.S.C. § 3110(a)(3):
"relative" means, with respect to a public official, an individual who is related to the public official as father, mother, son, daughter, brother, sister, uncle, aunt, first cousin, nephew, niece, husband, wife, father-in-law, mother-in-law, son-in-law, daughter-in-law, brother-in-law, sister-in-law, stepfather, stepmother, stepson, stepbrother, stepsister, half brother, or half sister.