The short answer is no. USAA membership is only open to current or former members of the military. Unless you are now, or have been, a member of the Army, Navy, Marines, Air Force, Coast Guard, National Guard, or the Reserves you are not eligible. If you are the widow, or widower, of a service member and had USAA auto or property insurance while they lived you may join. If you are the ex-spouse of a USAA member and had auto or property insurance while you were married, and have not yet remarried, you may join. If your parents have or have had USAA insurance, you may join. In that case the answer would be yes, but not because your brother is a member. It would be because your parents are members. While USAA is great insurance, it is only available for the military and their immediate family. So, no, you can not join USAA if your brother is a member.