Why Grisha Yeager and Frieda Reiss is an integral part of Eren and Zeke's journey in Attack on Titan Final season part 2

According to the preview shown at the end of Episode 3, the next episode of Attack on Titan Final season Part 2 is set to feature a revelation to the Yeager brothers, Zeke and Eren.

grisha yeager – RABUJOI – An Anime Blog

How did Grisha see Zeke in episode 79 of Attack on Titan? - Quora

You're not alone (Attack on Titan) - Chapter 5: Nemesis - Wattpad

grisha yeager – RABUJOI – An Anime Blog

Why Eren Yeager's actions in episode 4 of Attack on Titan final season part 2 change everything

In Attack on Titan, why did Grisha kill all Reiss family memebers, after all he needed only Frieda's Founding titan? - Quora

What did eren show grisha to convince him to give eren his titan? (Before the retcon) : r/titanfolk

Attack On Titan: Titan Shifters Ranked By Age, From Oldest To Youngest

Attack on Titan: Final Season, Part 2 - The Ultimate Recap