Shingeki No Kyojin: The — Final Season Episode 10

Pass the to someone of royal blood. This required Historia Reiss to inherit Zeke's Titan and bear children to ensure the royal lineage continues.

In the present day, Historia is shown to be pregnant, which effectively delays the military's plan to have her inherit the Beast Titan immediately upon Zeke's arrival. Shingeki no Kyojin: The Final Season Episode 10

In the past, Eren vehemently opposed any plan that sacrificed Historia or treated Eldians like "breeding stock". This stance marks the beginning of his radicalization and eventual split from the military's slower diplomatic approach. Pass the to someone of royal blood