I can never remember how different they're making Kryptonian and Terran DNA at any given time. That doesn't mean they'd have Lex Luthor (or Paul Westfield)'s DNA on file, though. F- blood type? LOL. The failing a blood test line sounds so Kon. From a purely biological standpoint, though, I imagine that if Kryptonian blood cells had different antigens than the usual (for Earth humans) A, B, or lack of either, they'd probably call the Kryptonian one C. If he got an O gene, for example, from Lex and a C one from Clark... his bloodtype could conceivably be C-. *giggle* Do you know what Lex's blood type is supposed to be, anyways?
Thought! Batman got a DNA sample somehow. He knew who Kon's other genetic donor was because of it, but was too paranoid to tell anyone. He didn't decide he doesn't like Kon because he's technically a metahuman but because he's Luthor's kid. Hm...