Ah jeez. No bueno. Definitely not hacking, and definitely sounds like some kind of delusional disorder...
As a person who has a brother who dealt with very, very severe OCD and still deals with mild-moderate OCD and who is very likely regressing due to his lack of progress due to him not being honest with his doctors due to him feeling ashamed of his disorder, keep up the good work. If you can/are willing, meet with the doctors and fill them in on the things your cousin won't, but keep attempting to convince him to, as well.
This is some pretty heavy stuff, good on you for stepping up.