its quite normal unfortuantly.
Doing nothing makes you tired... litterally. When people loose their routine, loose focus, loose confidence, etc. its all just a slippery slope thats harder and harder to get out of.
The answer is to keep routine alive, keep working, keep moving and keep pushing, even if its not in the areas that you want it to be. If I were advising you and your parents it would be that you should keep forcing him to do stuff.. give him jobs, give him responsibilities, give him tasks - and don't accept his crap when he doesn't want to do them. It doesn't matter what they are, they don't have to be huge or revolve around money.. just things to keep him going.
Once he is up and about doing stuff most days, then you can look towards the future and make a decent plan to help him get a job - maybe study some more, maybe change fields of interest etc.