Sexual Abuse Support Group
Sexual abuse is a relative cultural term used to describe sexual relations and behavior between two or more parties which are considered criminally and/or morally offensive. Different types of sexual abuse involve: Non-consensual, forced physical sexual behavior such as rape, incest or sexual assault, or psychological forms of abuse, such as verbal sexual behavior or...
You have been through so much please don't add guilt to the load. It doesn't look like you did anything wrong. Sometimes kids are more of a discipline problem for the parent(s) they feel more safe with. That could mean he was feeling not safe with the grandparents for some reason. That is just a wild leap...I am not saying the grandparents did anything that would cause his behavior either.
Sometimes kids are just wired wrong...who knows. But from your story it appears you were in a very difficult set of circumstances with an unruly teen and dealing with it the best you could. I can't see where you did anything wrong.