User blog comment:FairyRaven/Fairy Tail Chapter 414: Drops of Fire, Review and Commentary/@comment-1776824-20150105154224/@comment-1776824-20150105160657

Ahh, those are fair points. But there is a very clear connection between the two at the least, hence why Zeref keeps alluding to the choice Natsu will have to make. I mean, Igneel chose not to kill him, and Zeref and Natsu know each other from a time long since passed (which Zeref apparently only remembers), but I guess we'll see what happens in the future~