There are two things here. How do you manage to make him take medicines? And other issue is that however long the treatment may continue or whatever no of doctors you visit, if proper dosage for an adequate duration is not ensured , there won't  be good improvement. 

hi, it seems like he is suffering from paranoia. please visit a psychiatrist and start medicines after a thorough evaluation. also please please visit a psychologist, get psychological testing done and seek therapy. both medicines and therapy will get a positive effect on him. take care.

Hi, from what you have described, your brother is suffering from  Paranoid Schizophrenia. It is a long term Psychiatric disorder and one of the few Psychiatric disorders that is treatable , but medication needs to be continued for a long period of time and sometimes lifelong, hence we do not call it curable. Intelligence is not affected and has nothing to do with the illness. Schizophrenia can even affect IITians! However, there are very good medicines available to treat Schizophrenia and with family support and rehabilitation, a Schizophrenic can lead a completely near normal life. They can work, earn , marry , have kids etc. The only thing to be kept in mind is that they should take the medicine regularly. Please consult a good Psychiatrist and start proper treatment at the earliest. Hope this helps, All the Best!

Hello there..... Treatment of paranoid schizophrenia involves a lifelong commitment; no cure for schizophrenia exists. Treatment, essentially the same for all types of the disorder, varies based on symptom intensity and severity, patient medical history, age, and other individually relevant factors..... Consult Psychiatrist....