Thanks everyone. I think I gave the wrong impression that the situation is more about workplace gossip and that I'm trying to stir up drama. It is to some extent. But that was just to give context. This isn't an attempt to pry into his personal life. I do, however, intend to get to know him better. I'm genuinely interested in him. Thanks to his close friend I know with relative certainty that he's neither gay nor in a relationship. So these possibilities are pretty much out of the picture. It's not that he's trying to avoid workplace romance. It's that he's trying to avoid romance, period. And he's not shy about discussing other aspects of his private life. He's pretty much a nerd, massively into computer games and comic books. He sometimes talks about his family, his hobbies, even his physical health and the surgeries he's had (not to me though, we don't share the same office space). When I said "The rest of his life is a mystery to everyone" I meant his love life. His friend tells me whenever they ask him about it he shrugs it off by saying "I dunno, it just hasn't happened yet".
I understand your concerns about his privacy and your criticisms. But what if despite the appearances, he's romantically awkward? Maybe he's not good at picking up indirect advances. What I'm trying to say is that maybe he's not avoiding for the reasons you guys mentioned. Maybe he's just shy. If that's the case, how can I approach him? If you guys seriously think I should drop it, then I will. I don't think at this point I'm clear-minded enough to make the right decision anyway.