Welcome to HealthcareMagic.
It is possible that your brother has some psychiatric disorder.This can be a long term disease or a short attack of psychosis
due to some stress
I advise you to visit your Psychiatrist
and let your brother express his thoughts to the doc.Clear history and discussion is compulsory to come to any diagnosis.
Big task for you is to convince your brother to visit Psychiatrist.
If you need more information feel free to mail me.