Choso and Yuji are half-brothers through their shared parent, Kenjaku. Kenjaku's ability to control bodies allowed him to be both Yuji's mother and Choso's father. Yuji's connection to Choso ...

Yuki reveals her powerful technique, Star Rage, in a rapid and engaging fight against Kenjaku. Choso's sacrifice and Yuki's persistence make for a compelling storyline, although Yuki's potential ...

and Kenjaku probably knew that, hence why he built his plan around that. It also helps this theory that Choso and his brothers didn't have any memories of their mother in Jujutsu Kaisen ...