I joined in '87 while on AD, and over the years I have been able to extend an invitation to join to other family members (i.e parents, wife, sister, brother, cousin). My cousin was part of my household at the time of the invitation. My sister, brother, and parents were not although we do share the same last name. After my cousin got married she had her husband joined as well. One of my buddies extended an invitation to his roommate and that person was approved. I don't know if the rules have changed but it seemed as long as you could proved someone was related to you or lived with you that those people qualified for membership.