Much more likely

I think this one is more likely lol, but I would love to see Kristin again!

What if she is the sister of neither? Why does she have to be either Regina or Maleficent's sister?

I don't know, but I did say they were just theories... ^

I think so.

I can't imagine Regina's parents (neither Henry sr. nor Cora) doing a child with somebody else.

Cora would ;) There are a lot of theories saying it's Rumple and Cora's child ^

Cora would have been together with Rumple after she ripped out her own heart? That's impossible! Rather I believe Regina is Rumple's daughter.

I would hate for Regina to be rumple's daughter since I love her and hate him haha. I think WW could be cora and rumple's daughter, sounds likely. Also it's not impossible, when you think about it. Cora didn't love Henry Sr and it always depends on how old the WW is.

Nah, another relative of Rumple who will turn against him... would be really cruelty.
True, Cora didn't love Henry sr. But after refused him, Rumple didn't want Cora. Rumple is more prouder to acquiesce a one-night affair with someone who didn't consider him worthy to herself.

Haha, I wouldn't mind. Plus, we don't know how old the WW is in OUAT, they made Ruby like 5 years younger than what she actually is so it could go anyway in OUAT.

:) Actually, I'm glad the Wicked Witch will be the new villain. No matter who are her relatives.

The witch may be Rumple and Cora's daughter

Idk, they really haven't mentioned anything about Regina having a sibling, they never really even implied it. Plus it wouldn't make sense that she never showed up in The Stable Boy or any of the other young Gina flashbacks. Where as Maleficent doesn't have much history or background so there's room to add such.

There are links to why she might be Gina's sister. ^

Makes more sense

Maybe she couldn't be with her parents for some reason who knows? But it seems more likely Regina cuz she's a main character and stuff tends to be linked to her

I can't wait to see the Wicked Witch on OUAT and the idea of her being Maleficent sister (for some reason) makes me even more excited, and it kind of makes sense since the Wicked Witch had a sister who was killed (I know Maleficen isn't dead but she's not really alive too so I don't know :P)

I hope it's Maleficent's sister.

Because she looks like her and she doesn't look like Gina... but she could also be Rumpel's and Cora's daughter: how awkward would that be for all the characters? lol

I just don't see how it would work with WW being the offspring of Rumple and Cora.

When Cora ended their relationship, that was it. I don't think Cora would have gone back to him and I don't think Rumple would have gone back to her. Rumple even went so far as to help Regina so she could defeat Cora. Also, between all of the flashbacks, there was never even a hint of Regina having a sibling. And unless Cora went away for a really long time, I don't see how they could piece everything together without it seeming like they just pulled it out of thin air. Because it would definitely be noticed by Henry, Sr. and Regina if Cora were pregnant again.

As mentioned before, though, Maleficent has little to no back story and there's a lot more room to work with. If WW was to be anyone's sister (or half-sister), Maleficent would make sense. Plus if Maleficent and WW were close sisters, then maybe the WW wants to take revenge on Regina for everything she's done to Maleficent. There's just a lot more room for possibilities, whereas the other theory (WW being Regina's sister) would be hard to work out without having details contradict each other.

^ Yeah, exactly my point too

I think, we forgot about the time that Cora spent in Wonderland as Queen of Hearts. Wicked Witch came from the Realm of Oz. It's possible (hardly believable but possible) Cora found a partner for herself. And the fruit of this relationship is: the Green Lady. :)

She could be the sister of neither. xD But yeah like zanhar1 and matchesrulezu stated, we know almost nothing about Maleficent's past so there's a lot of that to explore. ^.^ Would love to see Kristin Bauer van Straten back too. :P