Hi you don't say how old he is, has he always stayed with you ? It could be he is doing all this for attention or he feels angry and what he is doing is the only way he can deal with his feelings. Teenagers can be a nightmare and we tend to forget that they have a lot to deal with. The other family he goes to, you don't know what he has told them and the mother may feel she is helping by taking him in. I know it may sound strange but my eldest had a friend who told us all sorts about her parents and I used to let her stay, though I would phone and say where she was. I din't know who to believe and I would rather she had ours to stay at than wander the streets. At the time I thought I was helping, 7 years on and a bit wiser I think I shouldn't have interfered, but at the time you do what you think is right, the other family may feel they are helping. I know it is hard, we have gone through a lot with ours, and sometimes you just want to give up. In the end we backed down and stopped re-acting and that seemed to help. If the police charge him that may be enough to give him a fright. Good luck. You will get through this believe me.