Do you have any opinion on the "dragonfly amongst the reeds" theory, ie that Jojen/Meera are descended from Prince Duncan and Jenny of Oldstones? I know the crannogmen are closer to the CotF than most other Westerosi cultures, but it could also explain why Jojen greendreams. Not sure if it would have a huge impact on the story if it was the case, but it'd still be something interesting. We have no idea if Duncan/Jenny had kids, assuming they did, they'd probably still get pretty good betrothals.
I sincerely doubt it. The history of the crannogmen provides a solid basis for Jojen’s powers without any need to get the Targaryens involved, and as far as I can tell, there’s no other direct evidence. Moreover, every relevant item in both the series and WOIAF indicates that Jenny was peasant-born, not a daughter of House Reed. After all, this is where the drama and dilemma come in for Duncan’s dad: “It was true that Aegon had been a friend to the smallfolk, had practically grown up among them, but to countenance the marriage of the heir to the throne to a commoner of uncertain birth was beyond him.”