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.

Attack on Titan/Shingeki no Kyojin - shinshinjane - Wattpad

attack on feelings — Favourite moments: Frieda Reiss

Eren Yeager Villains+BreezeWiki

Zeke Jaeger (Anime), Attack on Titan Wiki

Why did Grisha Yaeger scream out 'Is this what you want Eren' after killing the Reiss family? Was Eren controlling him? If so, how and why? - Quora

Rumbling, Attack on Titan Wiki

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

The Entire Attack On Titan Timeline Explained

Why Did Grisha Yeager Kill The Reiss Family In Attack On Titan? - Animehunch

Attack on Titan' Episode 79 Preview: Eren and Zeke Will 'Learn the Truth' in the Paths