Originally Posted by
Michael P
J'onn had a mate and children on Mars, so the best you could say about him is that, given Martian biology, their conceptions of gender, sex and sexuality are completely different from ours. But he definitely got it on.
Most of the characters you've listed have had sexual relationships. (Seriously, Starfire as asexual? She's just about the polar opposite.) About the only ones I could see as asexual are Darkseid and Joker, and do you really want them as representatives?