Board Thread:Spoilers!/@comment-413929-20150114222625/@comment-24674051-20150326132912

In thinking about it more, I think that making Emma be Mal's daughter, at this point in the show, would be too much of a twist. Had we been uncertain of Emma's origins, and just recently found out that she was most likely Snow and Charmings daughter, and had Mal reenter the picture at around the same time, I'd believe that. But we've had 3 1/2 seasons of Emma being Snow's daughter, and confirmation from multiple sources, including Rumple, that she is the product of Twu Wuv.

But, That doesn't prevent there being some sort of skullduggery involved that links Emma and Mal's daughter (presumably Lily).