Clark and Lois have a lot of past history pairings to plumb the depths of. There's also Jimmy, Perry to choose from when it comes to that as well. Sadly, Lex doesn't have the same past life pairing conflict that the others do (unless you want to go with one Fan theory that Baron Tempus is actually Lex Luthor in the same soul).
CLARK: No. I'm just worried I'm a jinx.
JONATHAN: A jinx?
CLARK: Yeah. Let's face it, ever since she's known me, Lois's been kidnapped, frozen, pushed off buildings, almost stabbed, poisoned, buried alive and who knows what else, and it's all because of me.
-"Contact" (You're not her jinx, you're her blessing.)
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