What do we do about my sister's financial abusive husband?

First of all before I continue I will say that I did tell my mom not to get involved but she didn't listen. We come from a immigrant background but the only person born outside of the U. S. was my mother. My mom has always had a heart of gold and has been a great mom, grandma and even mother in law. When my sister and her husband got married they only lasted one year living together. He told my sister he wasn't going to get a second job to support her and my niece. My mom decided for all of us to move in together. She said she wanted to help them. We have continued this way for years now. My sister husband doesn't have good credit so he asked my mom to get him a car and she did as she's done other financial things for them. My mom has also paid for stuff for my nieces if they ever needed anything. I know that the car is not what has caused him to stop paying rent and I know he's been like this since they got married. I have always known that only abuser would act this way. My sister and I come from very hardworking parents so we know when people are lazy. Her husband is was born here and even his dad used to the way he was. I know this because my brother in laws mom who has babysat my nieces has said this before about her own husband. Well my mom bought a house and they now live with us.

Updates
+1 y
After the whole car incident my sister's husband got mad because my mom had to take the car back because he wasn't making payments. He didn't have the proper insurance on the car and my mom's name was on the lease. Well it's been about a year after this and my sister's husband has stopped paying rent. I was wondering if my mom would've made him sign a legal paper about them paying rent would that help. I know that this is a small claims court and I also know that if he wants to he canleavewithem
What do we do about my sister's financial abusive husband?
Post Opinion