Theory: Grisha Yeager's and Zeke's(The Beast Titan) Relation (Spoiler Alert if you haven't gotten to the Uprising arc yet)

AcidBath said:
When the Beast Titan first appeared, there were lots of theories going about that Grisha Yeager, Eren's father, was the Beast Titan. Those ended up being false. Nonetheless, I think there are multiple reasons to believe that they are related. Just how closely? I suspect, as of now, that they are brothers. I've seen a few other members on here note similarities between the two in comments in past topics, and the topic has come up in passing on a few other sites, but I have yet to find a truly comprehensive review of why they might be related. So I'm going to attempt that right now:

1. They are both from outside the walls. This is a fairly obvious detail, but I may as well point it out again anyways.

2. They bear a fairly strong resemblance to one another (I pasted these pictures together for this btw):



3. They are both Titan Shifters. We don't know much about the people/organization outside the walls, but one thing we do know is that they have been giving the titan serum to children to accomplish some goal (wiping out what’s left of humanity inside the walls, or perhaps an ever bigger agenda that includes that?). Just look at Reiner, Bertholt, Annie and Marcel. Perhaps these two, who seem to be around the same age (given that their respective appearances were, at the least, 5 years apart), having a similar upbringing as brothers, were both injected as children to accomplish same said goal? Just a thought to entertain. It's tough to go much further with these details, given Grisha's hazy memory when he was found outside the walls, but just consider what we’ve got so far.

4. Not only do they bear a resemblance to one another in human form, but they also share some key physical characteristics in their titan forms:



Also consider that when Grisha was first spotted, there were oddly no Titans in the nearby vicinity (as noted by by Keith Shadis). My best guess is that he possessed some rudimentary coordinate-like ability to disperse them before he lost his memory. Zeke possesses this ability as well, using it to control Titans, having displayed it multiple times. This is probably the flimsiest evidence to go off of, but I want to note it anyway.

Given all of these reasons, I find it highly likely that these two are brothers, or are at least related. As of now, as I noted earlier, the details on who exactly the people outside the walls are are still shrouded in mystery. We don’t know much about their relationship to the Reiss family, as none of the characters from outside the walls have divulged that info yet. Grisha seemed to be very aware of what was going on when Shinganshina was first attacked, so we can assume that he largely retained the memories of his past life at some point. His possession of the titan serum, and knowledge of the Reiss family, confirm that. What I’m getting at is that to know all this information, he was probably originally high up in their hierarchy of command and/or power, like “War Chief” Zeke is. There’s still the mystery of the basement, which should shed a lot more light on this matter as well.

What do you guys think? Is there anything I’m missing? Do you think we’ll find out in Chapter 83? Please, share your insight as well.

02133991882yolo said:
I think the beast titan is grisha's first son. Cause they both look alike and as it mention in the last chapter that he got married with a desendents royal blood type woman and they both got a son named zeke. And when zeke's said that "you look nothing like your father" cause eren was most likely look alike his mother. And another proof is that when grisha want to do an experiment on zeke to make him a titan, and zeke betrayed grisha by reporting him to the mp's. So maybe after he reported grisha he tried to do it for him self and ate a person that could change into titan. And that was along time ago so... no wonder zeke's look so old.