I have a brother at 21 years old with no acknowledgement for prayer. His whole life is taken up by studies for University. He doesnt do anything for himself or anyone else. He makes my mum run to feed him, wash his clothes, everything etc. I was just wondering is it sin for us to do all these things for him knowing he doesnt pray or has anything to do with Islam.

You need to advise him, if it did not work, then it is not allowed to serve him.