Grisha: The Story of Cellist Gregor by M. Bartley

Could Grisha Jaeger be the Beast Titan? Could someone give for and/or against proof? - Quora

Basement, Attack on Titan Wiki

My brother ate my dad.” -Zeke Jaeger : r/titanfolk

Grisha had Zeke at 19 years old. Zeke was raised by teen parents. : r/titanfolk

Did Eren's father steal the Founding Titan to bypass the first king's will, allowing Eren to get rid of the world of Titans? - Quora

Eren's actions of manipulating Grisha and 'killing' Carla share the same goal. : r/ANRime

In Attack on Titan, when Eren asked the trainee squad teacher about his father, he said it has been 20 years since then and Eren has been a titan shifter for 5

Eren-Carla is special : r/titanfolk

Grisha's Shocked Seeing Old Zeke & Begs Him To Stop Eren

How did Grisha know that the memory he was seeing was from Eren? Didn't he only see the memory from eren's POV? - Quora