User blog comment:IamJakuhoRaikoben/Chapter 294: Battle of the Dragon Slayers, Review./@comment-3555799-20120804002715/@comment-4388213-20120804013304

Would make sense due to his connection to Acnologia, but I wouldn't be surprised if he's master the God Slayer style (due him possesing similar iris as Zancrow), but only time will tell.

And if the Dragons are in alternate world (like edolas) time may run differently for them, Natsu was probably chosen by Ignell to be his "son" and brought their. You also no pure dragon slayer except for Wendy has had their age revealed, my guess is they were all picked up during various time frames for what purpose...as Ignell said can human's surpass dragons