Hello,
Welcome to Health Care Magic.
We understand your concern.
I am Dr Alok Sinha,MD Psychiatry, from India.
I will try to help you.
I have read the symptoms of your brother in details. If your brother is like this since years then apparently he is suffering from some personality issues. Most of the symptoms you described here point towards
Borderline personality disorder.
A person suffering from this disorder usually show these kind of symptoms like mood swings, sudden change in behaviour, poor anger control, demanding nature, fear of abandonment etc. Although the treatment is possible but the biggest hurdle is insight. As a person of personality disorder have little/ no insight into his own behaviour, they usually don't accept having behavioural problem.
You should try your best to earn his faith and to make him believe that whatever you are doing is doing for his benefit. You may tell that you all love him a lot and want to see you in the form of a better person. Later on you may convince him to visit a
psychiatrist who may assess him in detail and may suggest few medicine for mood and anger control as well as some behavioural techniques to shape his behaviour.
I hope it answers your query. I wish your brother all the best.