What if Lois wasn't reincarnated as his great-granddaughter, but rather as one of her friends?
There was a movie, years ago, called "Chances Are" with Cybil Sheppard and Robert Downey, Jr. It was about a young father who dies in an accident and is reincarnated. When he reaches adulthood, he's drawn to his daughter, until he realizes who he was and then he tries to woo his (ex)wife. It seems like they solved the problem by having him no longer be related to them/remember who he once was (but it's been so long I can't remember how that happened).
It just seems like it would be less complicated (and definitely less squicky) if there was no blood relationship to contend with.
Lois: You know, I have a funny feeling that you didn't tell me your biggest secret.
Clark: Well, just to put your little mind at ease, Lois, you're right.
Ides of Metropolis
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