哥哥 (gē ge) is a noun meaning 'older brother' and is formed by reduplicating the character 哥, which on its own also means 'older brother'. The reduplication adds warmth, familiarity, and affection—making it especially common in family speech, child-directed language, or casual conversation among siblings. Unlike formal terms like 兄 (xiōng), 哥哥 is informal and intimate, often used when addressing or referring to one’s own older brother, or sometimes even as a respectful or friendly term for slightly older male peers or acquaintances.

The first syllable carries the first tone (gē), while the second is a neutral tone (ge), reflecting standard Mandarin reduplication patterns for kinship terms. It’s not used for younger brothers (that’s 弟弟, dì di) or for brothers-in-law (that’s 姐夫 or 妹夫). As a cultural note, using 哥哥 signals closeness and respect within Chinese familial hierarchy, where age order matters deeply.