User blog comment:FairyRaven/Fairy Tail Chapter 435 & 436: The Cry of Victory & Memoirs, Review and Commentary/@comment-24784846-20150518115847/@comment-125.212.122.245-20150518131446

I think that E.N.D. is more of Zeref's creation than his brother. It's like E.N.D. is the soul and Natsu is the body.