If your brother is neglecting your parents it will get worse. He will probably take their money as he takes over more.

This is what my older sister did with my parents and they gave her too much control. My brother and I complained to the state as we felt my parents were being bullied manipulated and did not realize how much control they were giving her. You should start looking into adult protective services. Idk if you live in the US or what is set up you can get in touch with before it’s too late.