I'm sorry to hear about your sister. I have drug addiction in my family, too. As others have mentioned, you can't do anything to control your sister. I think the best thing you can do in this situation is to all CPS. Tell them what you know. I know that's not what your mom wants, but it is the best thing for the kids. Did your niece receive any treatment after she was molested? As you know, it is dangerous for the kids to be around this sort of environment.