§1. A vicar general and an episcopal vicar are to be priests not less than thirty years old, doctors or licensed in canon law or theology or at least truly expert in these disciplines, and recommended by sound doctrine, integrity, prudence, and experience in handling matters.
§2. The function of vicar general and episcopal vicar can neither be coupled with the function of canon penitentiary nor be entrusted to blood relatives of the bishop up to the fourth degree.
Source: Code of Canon Law (Vatican.va)