I am so sad...

How do you sit back and watch people take advantage of your parents? My parents are in their 70's, and a felon just got out of prison and my niece (who lives with them also a felon) decides it is ok to have her "friend" over. She slept at my parents house. I worry for them. My parents are barely making ends meet and now they have 2 living with them that do not work and mooch. It is hard to sit back and not visit your own parents because of the situation. I am so distraught.
My dad has said that what he does is none of our business. But when do people step in and say enough it enough? I am at a loss and I feel so guilty if I don't do something. What is something horrible happens to them because of these druggies and then we or I did nothing? Guilt would take over and we would all say, we should have done something. The legal system is a joke. My niece keeps doing drugs and getting caught and should be in prison but probation don't care. Slap on the wrist everytime. Now this girl is living there. She is such a horrible person, she drank and drugged when she was pregnant and her boy is handicap. He has many many things wrong with him. She should be made to look at a photo of him each and everyday. Of course her aunt took that baby.
I am so sad because I have no parents. I feel so bad for my mom because she is in no place to speak up. I feel my dad has reverted back to a dumb teenager making wrong decisions.
My sister won't even step in, this is her daughter living with my parents and her daughters friend. I don't even speak to her. She should step up and redirect her daughter. We aren't talking about young people. My niece is 30 and has a kid and no job, except for the drugs she sells.
Ok I needed to vent somewhere....