"He was a lot of things to me" "The only conclusion was love"
Honestly the only combination that doesn’t “ick” me out a little is if EVA is related to Zelena, which makes Regina and Snow related (cousins), without the added ick factor. Eva’s brother could be Zelena’s father and the Wizard of Oz perhaps. It might explain Eva tripping Cora all those years ago , if she thought of her as “that tart who had the gall to break my brother’s heart”, not knowing the whole story perhaps of how Cora was pregnant, and run off by the royal parents. I don’t now, still soap-operaish but maybe a touch better.
If Eva is from Oz maybe she and Zelina and Glinda are sisters?