Among us three brothers, the third one is the smartest.
Tips
usage
Chinese families informally rank siblings as 老大 (oldest), 老二 (second), 老三 (third), 老四 (fourth)... continuing as needed and ending with 老幺 (yāo, youngest). Used affectionately within families and very common in fiction set in large families.
culture
In sports / business slang, 老三 can also mean 'the number three / third place' — e.g. 行业老三 'the third-largest player in the industry'.
