My parents were in your position some years ago. They had to get help and my brother never forgave them for that. Unfortunately, you don't have any rights, only if he does something to get him sectioned can you be sure he will get expert help. He cannot be made to go into hospital or take any medication. It is a very difficult situation for you, and heartbreaking too. It is not easy to watch someone you love with a mental illness, knowing that they are left in society, to do their own thing. My parents got a social worker involved, but my brother did not wan't to know. All you can do is be there for him, hopefully he will realise he needs help and come to you.
I wish you well with this, I know the pain it can cause.