My moms mad my brother won't talk to her

My brother is staying with me and my husband. My moms boyfriend was beating the fuck out of him and my mom was too strung out on meth to give a fuck. They took both him and her boyfriend's baby daughter. The little girl got put with her grandma and I took my brother. The police got called because he was beating the shit out of my brother for no reason besides being drunk then held him over the balcony and threatened to drop him. He's only 14 and has no strength so he couldn't fight back. My mom has been trying to call him but she can't seem to understand why he's upset. I told her she needs to give him his space and she's like "But Mike is sorry. He never meant to do it. He was drunk". Thats always the excuse. Mike is drunk, Mike is high, Mike is tired. When I had to go get my brother his whole arm was bruised because Mike through him down and stomped on it. He had two teeth knocked out and burn marks all over him. My mom is fucking delusional. My Nana has been my brother he needs to speak to her because at the end of the day thats our mom and we only have one. I'm gonna tell my Nana if she wants to continue talking to him to stop bringing the situation up. He will talk to her if and when she's ready. Mom called again bawling begging me to put him on the phone. I asked him, he said no and I told her. Now she's accusing me of trying to come between her and my brother and that my whole plan is to turn him against her. Like I said. Shes delusional.