I saw your other post about this, too.

I think it is great that you are trying to help your sisters, but I would be prepared for your stepfather to not be receptive to your suggestion that he get some help. Your mother is probably also aware of this situation, even if it is seems that she is not doing much about it.

It may be easier to convince your mother that she needs to do something to protect your sisters than to convince him that he has a problem.

The awful thing is that there may not be much you can do to protect your sisters. Your mother and stepfather need to figure this stuff out for themselves -- most parents aren't receptive to being told these sorts of things by their children.

I hope this works out for you and your siblings. It really sounds like a hard place to live