Dealing with depression

My 26 year old brother was born with cerebral palsy and he appears to be suffering with depression. In recent years he has become more and more recluse to extent where he rarely leaves his bed leaving myself and my family clueless on what we can do. He has function of his legs but after numerous operations and hip problems, movement has become more difficult for him, as time has went on he now relies on constant pain relief and struggles to do some tasks.
Growing up I always saw him as able as myself, we would play and go to the park just like normal children would. He was always very intelligent, loud, funny, outgoing and likeable, not a person you would forget easily!

To say the least we didn't have an easy upbringing but our mum did her best to treat him equally and provide him with everything he needed.
He has been to college a couple of times but struggled with this and never really completed a course and has also never had a job. He loves computers and really has a lot of potential in writing (as he's very opinionated :P), as well as having a love for music. He enjoys spending time with his many friends and going to music concerts in which he travels the world for. However, in recent years he has begin to shut himself out and is not really going out with friends, and has even stopped going to some concerts (which is really shocking, as this was life!!) to the extent where he lies in bed all day and he becomes really disinterested and depressed.
As a family we have all tried to encourage him but nothing seems to work, on occasions he has stated that he would like to get a job and have routine in his life but this enthusiasm is often short lived and the depression takes over again.

I believe he has the potential to live independently, although he would need some level of care, like with general cleaning. He struggles to bend over and pick things up and is generally off-balance, and if he were to fall over he would be unable to get up without some support, which I believe is also a great concern of his, one which I also find upsetting. He doesn't have the tendency to do things for himself, or do anything to help himself, and won't, as my grandad does it all for him.

I would like to get some help for him but don't know who to talk to or what the problems truly are, he doesn't really speak about things, it is difficult to tell whether his problems are related to depression or deterioration of his health, likely both, but his current lifestyle is really dangerous to both his physical and mental wellbeing. If he doesn't get help or change his lifestyle soon he is inevitability going to become very sick and very weak!

I am hoping to gain any advice on dealing with depression or living as an adult with cerebral palsy, I really hope I can help him before it is too late.
Thank you!