User blog comment:FairyRaven/Fairy Tail Chapter 465: 400 Years, Review and Commentary/@comment-9595671-20151207195152

I think Anna might be Lucy and Layla's ancestor possibly, after all since Layla was a Celestial Wizard and Lucy inherited her keys from her mom, it wouldn't surprise me if the magic itself has been part of their family line for a long time on Layla's side.

All the reveals though... those were awesome! Mashima knows how to reveal something and then surprise us by showing there's still more details to it. So Natsu can't destroy Zeref without taking his own life... that's tricky, even if it implies the remaining Tartarus members would go with him.