Your brother must be living the Oedipal dream. He's displaced his father and is living with his mother. Here's Rick Sanchez on that topic: https://www.youtube.com/watch?v=X-gHgcmFB6Q
In some ways, I feel as if my son, who is living with my ex, has done the same thing to me. Lol. But then I think, "I'm FREEEEEEEE!!!!!."