Also, Danielle, without breaking the confidentiality rules, there are things you can bring up with your brother's doctor to convey your concern that your brother isn't taking his medication. You may want to attend, if you live in the US, the NAMI Family-to-Family 12-week course where you get all the info and also a list of questions you can ask the psychiatrist without breaking confidentiality.
At any rate, I would call the p-doc and say you're concerned your brother isn't taking his meds.
Call NAMI's national hotline at : (800) 950-NAMI (6264).
Best,
Chri