User blog comment:Neetaku/Grisha Yeager is Alive/@comment-67.39.210.254-20150716141335/@comment-27082825-20150717170537

This seems the most accurate. That, or the fact that Isayama simply forgot. I don't feel as if Grisha is alive in anyway. IF he is, then there is some element from the equation somehow and we're in the dark. Which is possible after the whole "bloodlines" thing was introduced.