I don’t think they can, that’s why Hilary wasn’t the Attorney General, as I recall. I believe after RFK that’s not allowed.
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.
Passed in 1967, this was in reaction to Kennedy's appointment of his brother as Attorney General.