Board Thread:Spoilers!/@comment-2153169-20140402112823/@comment-24386552-20140411175638

Maybe when Leopold and Eva got married, they settled their problems by just simply talking about them and then dismissing them. Also, I think he met up with Cora again (if he is Zelena's father), and had a deal, and as long as they never mention their daughter (If they had a child together), they could go their separate ways, or maybe Regina's marriage to him was planned long before Snow was even born. Which is why it was never mentioned by Leopold or Cora, that they had a second daughter.