I think it’s possible (because everything on this show is) *but* I doubt anything will ever come of it for a few reasons. First and foremost, I doubt the writers plan on revisiting Zelena’s parentage anytime. To them, it was solved they’re more concerned with Zelena/Regina’s dynamic instead of Zelena’s family. Second, with that being said, they are also ignoring Zelena quite a bit recently and with all the stories coming up here in 6B (Gideon, the Black Fairy, Aladdin/Jasmine, Agrabah and Jafar, and tying up loose ends from the Evil Queen and Wish Realm) I doubt they’re going to revisit something they already told only to contradict it (this isn’t to say that they wouldn’t contradict themselves). And lastly, while the show has always had a funny relationship with incest, I don’t think they’d go all the way and make Zelena’s TL her own uncle.