It sounds like he has narcissist tendencies, if not full blown NPD, and from what you've said, he was probably raised by one (or two). Getting him to realize what's going on with him will be a huge challenge, and I'm not sure it will work. NPD's are notorious for not believing anything is wrong with them, their lives or how they perceive others around them. It's sad, because they are hurting worse than those around them that they hurt.

I wish I could offer words of advice or at least suggestion for convincing him....all I can suggest for you is to read up on Narcissist Personality Disorder, and for good measure Borderline Personality Disorder (which he also seems to be showing traits). It won't make him see he has a problem, but it might help you understand him, and hopefully help you and your siblings deal more successfully with this very unpleasant, sad situation.

Good luck and take care *hugs*