WARNING: The following contains spoilers for Attack on Titan Season 4, Episode 28, "The Dawn of Humanity," now streaming on Funimation, Hulu and Crunchyroll.
Attack on Titan's Eren Yeager and Historia Reiss have had a complicated history together. Ever since the former started opening up more in Season 3, the latter started caring for her more as a person and wanting her to live her best life. Eren and Historia have grown so close since then that many AOT fans ship the two of them over Eren and Mikasa; there are even rumors that Eren is the real father of Historia's child. As close as these two are, there may be a Yeager with whom Historia shares an even closer connection-- Eren's father, Grisha.
Narratively, Historia is destined to share the same grim fate as Grisha Yeager. Eren, however, recognizes this possibility and seeks to rectify it. The parallels become especially apparent during the finale of Attack on Titan: The Final Season Part 2.
In a flashback in Episode 28 of The Final Season, "The Dawn of Humanity," Eren talked with Historia about his plan to initiate the Rumbling. Historia was naturally against the plan; she would rather go with the Eldian Military's plan, which involved becoming a Titan, eating Zeke, bearing children, and eventually, being eaten by said children. This option was by no means in her best interest, but at least the rest of the world wouldn't have to die over it.
Eren, on the other hand, was opposed to Historia's inclination towards self-sacrifice. He always wanted to be sure that she could live for herself, which she definitely couldn't do with the Military's plan. He also mentioned that he didn't want to let the cycle of parents being eaten by their children continue. The latter point is where the connection to Grisha can be drawn.
At first, the idea of "children eating their parents" seems like a parallel to Ymir's life. She too was fed to her children in order for the powers of the Founding Titan to be passed on. This tradition was continued for generations as the Subjects of Ymir became what they are now. However, Eren's comment might revolve around something a little more personal.
Eren himself was forced to turn into a Titan and devour his own father. When he first realized this, it drove him crazy and left him racked with guilt. It's likely that Eren made his comment about children eating their parents with his own traumatic experience in mind. This would certainly explain why he's against the idea of Historia feeding herself to her own children.
In a way, Historia and Grisha are also both accomplices and victims of Eren's plan. While they're both made privy to Eren's true agenda, neither of them really wants to go along with it. They hate the idea of consigning to a grim fate, but they also realize that Eren's alternative is much worse. Regardless, they are both inevitably coaxed by Eren into complying with his plan. They both have regrets about their decisions to follow Eren, but eventually learn to live with them.
While Historia and Grisha don't share the exact same fate, they very well could have. Ironically, it's Eren who both causes and prevents the cycle that would connect the two from repeating. If these two victims of fate had somehow met, they would have certainly had plenty to talk about together.
