Board Thread:General Discussion/@comment-4821842-20161130061236/@comment-25375217-20161130061550

Hm... interesting thought. What exactly counts as Henry being Rumple's "undoing" has been debated, so... The general consensus is that it has to do with Rumple's death in Season 3A and fall to darkness after that (at least, that's my understanding of the general consensus), but this would definitely make sense, too.

Keep in mind that Pan was referring to Belle being "fertile" back in Season 3 when the undoing thing was a big deal. They may not have had Gideon, the sleeping curse, the dream world, etc. all in mind at the time, but they certainly could have already decided that the prophecy was actually referring to Rumple's second son.