During his journey to become the next King of the Pirates, One Piece's protagonist Monkey D. Luffy encounters a wide variety of characters, ranging from well-intentioned outlaws, dastardly Marines, and everything in-between. However, minus his crewmates on the Straw Hat Pirate crew, none of the people that Luffy runs into mean more to him than his adopted brothers, Portgas D. Ace and Sabo. This trio meet as children in the Goa Kingdom, but the full extent of their relationship isn't revealed until well into the events of One Piece's narrative.
Source：https://www.cbr.com/sabo-first-appearance-one-piece/
