RAD and sibling groups?

I have adopted two separate sib sets of three. First three were ages 2,3 and 4 when they came home. 2 1/2 yrs later we are now getting dx of RAD on the youngest and middle child. The oldest was spared RAD I believe only because his autism prevents him from even realizing that someone was suppose to be taking care of him. The oldest is very connected to the middle child because, being only 11m apart, the middle became the caretaker. These two RADishes are mild to moderate. Yes I do feel that even though we are only now getting dx that they are beginning to attach...its early so we will see.My second set were 11m, 3 (almost 4) and 7 at the time of placement. The oldest two came with RAD dx. 11m old got a RAD dx at the age of 2. The oldest was the caretaker and was very parentified. The 3 yr old was a rager, loved fire, punched and was cruel. The 7 year old is a master manipulator, couldn't tell you a favorite food, item or color if her life depended on it. Only will answer what she believes you want to here. She is just now starting to bond but boy is it a weak one. I fully expect her, at this point, to go back to her bio's at 18. I haven't ever had a true hug etc in 2 yrs. I don't expect one in the near future either. This week the 3 yr old is now starting to hug, true hugs :) , and has been a peach. Hoping that he is healing and really doesn't have bi-polar (isn't that horrible that I feel that it could be a fluke that he is healing) The 2 yr old is healing but refuses to allow anyone to do anything for her. Survival of the fittest and I am glad she did but WOW she is a challenge. They have a very strong bond and come to each others defense often. I am hoping that they can learn to bond with us but the reality is we are the parents and parents are scary and can't be trusted! Their sibs have always been there through thick and thin. The sibs have proven reliable. We have a long journey. I don't think I can honestly state that it does make a difference if they are bonded to the sibs. Only time will tell.