I just spoke to SOG yesterday about this same subject. We are going in June with my husbands entire family and need 5 rooms.
I was told that each ID card holder over the age of 18 can reserve 3 rooms. Which means, my husband can reserve 3 and I can reserve 3.
So if your brother has a spouse they can each reserve 3 rooms or your husband can get 3 and your brother can get 3. (Remember, your room rate is based on rank and DOD employees rate is higher) Once you check in, all non ID carrying people will be issued a SOG ID for the length of stay which will allow them access pass the guard at the entrance and to purchase tickets and things at the store without the Military member needing to be present.
We haven't decided for sure on SOG. We usually stay at one of the Disney resorts and really like how effecient the transportation is. (Last stayed at SOG 1995) Haven't heard the best things about SOG transportation since they reopened and are waiting and hoping that things will improve.