User blog comment:MeDeoPal/On the Origin of Titans and Shifters/@comment-110.32.149.5-20150725163910/@comment-24930713-20150725202315

Eren's father, Grisha Yeager, is not the Beast Titan. His affiliation with Reiner and Bertolt is not clear, but given the events of the recent chapter, it is extremely likely that he is from the same village as them. There are various theories about Grisha's, and the others, reasons for attacking humanity. But for now they are just that, theories, only time will show which one is closer to the truth.