RAD and sibling groups?

I am VERY new to RAD parenting myself. We adopted a sib group of 3 ( 4,5,&6 at the time) They seemed very bonded to each other...fast forward 9 years... They still seem to have somewhat of a bond to each other but have not attached to DH or myself. We are just now getting a RAD dx. So I am interested in what seasoned RAD parents have to say also.