It can work… just make sure the essay is about YOU, not your brother. Not his history, his hospitalization, his addiction, etc.
Picture the reader as deciding, based on your essay, whether he/she would like you as a roommate, judging whether and how you would contribute to the campus community or greater community, and answer some other unspoken questions. Show, not tell.
There are other posters on these boards who are real experts at this. Hopefully they will chime in.
@Lindagaf ?