User blog comment:Stone Roger/Natsu and Zeref have somekind of relation?/@comment-125.212.121.11-20130610120525/@comment-7418318-20130610121204

There is that as well.

To elaborate a bit on the point FTGM just made, Wendy immediately recognized the traits that Grandeeney and Porlyuscia have in common.

I didn't notice any traits that Zeref and Igneel would have in common and Natsu's only reaction to Zeref was "Who the hell are you. I've never met you" not "You seem familiar".