I know that going through the court procees may seem onerous to you but it really is the best way that you can protect your brother in this situation.  By having the court award you temporary custody you would be able to make legal decisions for him as to school, medical, etc., while your parents are unable to do so.  California laws can be complicated.  You parents may be able to consent to temporary guardianship as well but it really depends on the facts of the specific case.  Good luck.