My girlfriend's son just turned 18 in April 2013. I see that he is abusive to his mother, his grandmother and his great grandmother, and to myself as well... he manipulates them to no end and she doesn't think she can legally kick him out Can she?

I'm saying this because I was in a ysituation to where I married a guy like that. After a while, he did the same to me. He knocked me unconscious a few times, fractured my neck in 2 places leading to problems I still deal with 15 yrs later. The end came when he abused my 4 yr old autistic son and my younger daughter asked why we were still there. I left the next day. There ARE WAYS to stop him. File a complaint!