Well it is very possible he inherited a bunch of genes that makes him quite unable to cope with things well. I think there is more than just bad habits going on.

Schizophrenia can make you very, very passive. People can even inherit those genes without having the obvious symptoms of schizophrenia. Some schizophrenias are negative symptoms only. Being so frightened socially he would maybe be diagnosed with something like schizotypal (not that I "believe" in that diagnosis personally...).

You are correct he probably needs health care. It's very hard to make people go against their wishes, I know that first hand. I'm not sure about what system you have over there, but if he could be assessed at home that would be easier. IDK if a social worker could help where you're at?