Which mental illnesses would include this?

It's not just attention, though. His thinking and understanding are truly "off" at times. He has done illegal things as part of his "pretending". He has even treated one of his own children as though they weren't his because his thinking is "off".

I'm not asking for a specific "diagnosis", just different mental illnesses that such characteristics may include. He was at one point diagnosed as a schizophrenic, which could be the "weird" thinking, but I don't think schizophrenia covers the constant deceit and trying to come off as normal (his words at one point). He thinks he will be seen as normal or likeable if he portrays himself differently.

I should maybe add that this man is in his 50s and has been this way since at least his teens. He has been on meds that helped--but then went off of them because he was convinced he didn't need them anymore. I'm not talking some 20yo who's trying to impress people, but a man who has one failed relationship after another due to the deceit and abnormal thinking. He convinced one psychiatrist that he has multiple personalities, but he's smart enough to be able to pretend to have all of these different things.