RAD and sibling groups?

Wow. I really hadn't expected so many worrisome replies. It always seems like the focus is on keeping siblings together...I didn't expect so many replies to focus on separating them so that they can heal. DFS was neglected. I *know* that does not bode well for attachment issues (as with most problems that will land kids in foster care, I'm sure). That being said, he does actually seem to be attaching. He has real emotions - a lot of angry ones, but they are very real. He can be truly compassionate, and we get real hugs. He has recently said that he loves me. When he came, he was *perfect*...and then he rebelled. But, he also went from withdrawn, to SOOOOOO much more outgoing. So, it doesn't SEEM to be a pre-RAD honeymoon. A lot of the people with kids who are on the RAD spectrum (if it is a spectrum), say that their kids don't have favorites or preferences. DFS LOVES "Cars" (the movie), the color blue, and riding his bike. He HATES green beans. This is very different from everyone else in our family (he's not mimicking anyone - he's an individual in this stuff). DFS is making a LOT of progress. Part of that may be his personality. But, I cannot overlook the possibility that part of it may be because he IS away from his siblings. He is with three other well-adjusted (comparatively!), well-bonded and well-loved kids - and he is turning into one of them. I do have an innate worry that, if we were to bring his sister into the equation, it might re-create an "us-vs-them" type survival situation. I desperately want to do what is best for him. I *know* we could not handle the older two - it is not even in my long-term planning to reunite them as a sibling group (if it goes to adoption). But I struggle with whether bringing his sister in would be the right thing to do - for either of them. She has a lot of needs, too. Perhaps it would be best for the four of them to be separated - if they are EVER REALLY going to heal...not just survive.