User blog comment:CNBA3/My Big Three Theories!/@comment-203.215.121.203-20150218051254

Year 686(?) - Fairy Tail founded by Mavis and comrades (105 years ago according to Warrod Cken - ch. 342)

Mavis and Zeira were about 12-13 years old.

According to your theory, Zeira gave birth to Natsu maybe when she's 18+ years old, so Year 692+, Natsu's age is unknown but he has a body of 18 years old. So, unless Natsu was born in year 692+ and that he was frozen in time and resurrected in year 767 or whatever, your theory is impossible.