弟おとうと分ぶん

noun

sworn younger brother; junior male peer

Refers to a male treated like a younger brother in a hierarchical relationship, such as in a gang, club, or workplace. Not a biological sibling.

• 彼かれは組くみ長ちょうの弟おとうと分ぶんとしてかわいがられている。

  He is cherished as the boss's sworn younger brother.

• サークルでは、彼かれが一いち番ばん年とし下したで、みんなの弟おとうと分ぶんだ。

  In the club, he is the youngest and everyone's junior peer.