You can expect big problems and no privacy. This is such a deplorable idea. To me, it borders on abuse. Plead for better arrangements.
My family is moving to a smaller place and i'm gonna need to share a room with my younger brother and I was wondering if other girls had to share a room with a male family member and what should I expect?
How old are you? I would seem that the greater need for a room would be by the girl. Maybe you can get your parents to check in to the matter. They may not have looked at the long term affects of such an arrangement.