My mom has taken on my brother's two children in the interim while he deals with social services, for getting in trouble with the law. She's in her 60s, and she's handling a 2-year-old and 7-year-old, while working full time. I'm proud of her.
Your mom must be a strong woman.
I love her. She has so much patience to deal with it all, and she does it all with kindness, and tries to be as loving as possible to the children. But I wish she were harder on my brother. Sometimes I feel like she enables him, by how much she helps him, and prevents reality from slapping my brother in the face. Either way, she's a great woman.
That sounds so troubling.  You should get on your brother's case.