Sadly I don't think anything can be done (by you) about the daughter. Having been in an abusive relationship, people constantly tried to get me to leave but I had to do it for myself and gain the self respect to realize I didn't deserve that. All you can do is help her realize that she does deserve better. Also, if he really is that scary, she may be afraid that if she does leave he will come and find her and possibly do even worse things. I know that when I finally left my ex I had to park my car in random places and have friends pick me up and drop me off because I was terrified to be around my own car because he had threatened to be waiting at it for me.

The child is what I'm worried about. If you feel that there is inherent danger in him being around the children then call children or human services. That is their job! I know that would mean the children would also be taken away from your daughter but maybe, if she sees that he isn't fit (according to the gov't) to take care of their children, maybe she will realize how terrible he is?

Cutting her off from family and taking her away whenever something doesn't go his way is an absolute sign of abuse. Whether he physically abuses anyone in the household or only emotionally, they are both unacceptable. Unfortunately, many women won't listen to their family when it comes to these things. I know I didn't. What's even more sad is that most people don't call the cops when they hear or suspect spousal abuse. Go to Youtube.com and search for POWA ad. This guy did an experiment where he played drums all night and watched as people yelled at him to stop. Then another night he blasted audio of a woman being beaten by a man and no one called the cops or came to see what was going on. That video about made me cry.

I sincerely hope things work out for your daughter and the children. He sounds extremely dangerous. I'm glad that you recognize the signs and want to help!