User blog comment:Stone Roger/Natsu and Zeref have somekind of relation?/@comment-24.155.105.190-20140120023252/@comment-7418318-20140120094159

Maybe in a D&D setting where many Dragons have the ability to temporarily transform into Humans-shape at will, but based off of the facts we know from the Fairy Tail series so far, that's not possible in FT.


 * Igneel was the King of Fire Dragons at the time the seven invading Dragons originated from, before the Dragon Civil War.
 * Dragon Slayers were first created during the Dragon Civil War.
 * Acnologia was a Dragon Slayer and was Human until he transformed into a Dragon.

So since Dragon Slayers didn't exist before the civil war, Igneel can't be a transformed Human and thus can't be related by blood with Acnologia.