Sibling seperation...sorry so long and first time post

Helo and thank you for the forum. I am a foster dad from AZ. My wife and I have no bio children and one failed private/family adoption. This is our first foster care placement. We have been married for 18 years. I have been mostly reading on here for over a year and think I need to post. We have been foster care for a sibling group since 12/07 (2f, 4f, 7m). From what the folders state the 7 year old boy was given custody to a family friend soon after he was born. The two girls appear to have been with their bio mom, ther was no other information (other than looking up public court records showing CPS involvement since the boy was born. Drugs, no water, no foor, no electricity in AZ). We took the three in and then foud out bio mom was pregnant. CPS inqured if we were interested in the newborn but we had already full with out first placement of the three. The youngest was slow to bond. She did not want to be held unless you were standing up. She seemed happy, smiling alot. She gets along with both other kids. She dows not talk much yet, only a few two word combinations and mostly one word sentences. When removed from the other two kids she really opens up and talks more. The two older siblings have been in trauma therapy. The boy was definitely beaten and most likely some sexual exposure. The girl appears to have some trauma and sexual exposure as well and has been diagnosed with RAD and ADHD. The girl NEVER goes to bed without crying, popping in and our of bed, sometimes/most of the time sneaking into our bed. The boy has shown agressiveness towards the girl starting with putting his genitals on her stomach once, peeing in toy bins, on toys, on the girls room floor, on his floor. He constantly complains about her. She has done some things such as expose her self to me, touch herself in front of me, tried to put my hand on her genitals while sitting on my lap. She has made our dog yelp numerous times, we have not seen what she is doing to him. She does what she wants instantly without thinking about consequences or other peoples feelings. The boy withdraws very quickly. He will shut down at the first feeling of saddness, anger, fear and this is can happen doing homework, getting ready to go out, in the store, anywhere. The person he thought was his mother beat him, used him as labor and that is all we know for sure. There is a scar on his back that looks like a car cigarette lighter burn. The kids have just had a bonding assessment/best interest evaluation and it appears the psychologist is recommending the siblings be split removing the four year old girl. Real feelings or not (RAD) the girl appears to have bonded with me and I do have a soft spot for her. The boy seems to try to copy the behaviors of the girl, sitting on my lap, holding my hand, but just seems to go through the motions. The 2 year old is just starting to cry for daddy sometimes. I am already upset just thinking about loosing her. My wife thinks she is the cause of most of our problems and thinks I have been fooled by her. I just believe she is doing what her short life has taught her and we should have patience. I know it may be better for her and all the kids to be seperated so each gets the individual attention they all need. It just seems unfair and sad to have put these kids that were seperate together and now have to undo the mess. Just saddened and needed to share I guess. Robert