got a call - first respite

You might want to check in to more details re: the issues with the other boy. I.e. who is hurting who? In my experience, generally it is the more challenging child that is moved to forced respite. Just don't want you to be surprised. Even if he is difficult, he will likely be fine for a respite situation, and if his issues are security based, might do better with you than having to share with another child.