User blog comment:Stone Roger/Natsu and Zeref have somekind of relation?/@comment-90.221.52.199-20140316214948/@comment-49.146.230.40-20140421093105

We had the same thought :) but it could also be that Natsu was actually Zeref and Zeref could be Acknologia and they're all part of E.N.D the book of the beginning of time and space. =)