弟分

1. Origins, structure, and basic meaning

• Structure: In 弟分 (おとうとぶん), younger brother 弟 and relational part 分 combine to denote a junior protégé.
• Basic usage: 弟分 is someone treated as a junior or younger-brother figure within a relationship or group, regardless of blood relation.

2. Common pitfalls and similar expressions

• Junior protégé versus younger brother
  • It differs from a biological younger brother, 弟.