I'm an Occam's Razor kind of guy, so I'm guessing we'll find out that Luke was indeed her father, and she was the result of a brief fling he had with Keri Russell's character Zorri Bliss. Keri's in her mid 40s now, so she's old enough that it's believable. Keri & JJ go all the way back to Felicity together, so I could see him giving her a much more significant role than some scoundrel that used to run with Poe. I think that back story is a smoke screen.
I'm guessing we'll find out Palpy is her grandfather from a fling he had with the lady who used to clean his throne room. I mean he's old enough that's it's believable and he's certainly a scoundrel.
It'll be a bit like Arnie's illegitimate son - it harkens back to his glory days and started as an embarrassing accident, but he wants his offspring to follow in his footsteps, and they do reciprocate, at least for a while (that's evil Rey.) Just like Arnie's illegitimate son, Rey will flex her force lightning muscles like grandpappy.
Sorry, on second thought, this whole idea reads crazy.