Family is an important element for many Bleach characters. Even when family relations don't directly matter to the plot, plenty of characters have siblings around, especially the Soul Reapers. Yoruichi Shihoin has a little brother, and it isn't a total surprise. For one thing, she's a part of a major clan in Soul Society, and those families can take care of multiple children. Plus, she was never supposed to be clan head, so her brother was implied to exist because of that fact alone. Yushiro Shihoin has been a background character for a fair part of the Thousand-Year Blood War arc, and he's finally reunited with his sister.

Unfortunately, his reunion and attempt to help Yoruichi hasn't gone well for him. While Yushiro is clearly a talented fighter and able to hold his own against many enemies, he's nowhere near powerful enough to fight a Sternritter, let alone one of Yhwach's Elite Guard.