What episode does luffys brother pop in one piece?

Luffy doesn't have a biological brother in the One Piece universe. However, you might be thinking of Portgas D. Ace, who was Luffy's older brother, the son of the late Pirate King Gol D. Roger and Portgas D. Rouge.

Ace appears in the One Piece anime in episode 152, and plays a significant role in the "Marineford Arc" of the story, which spans episodes 456 to 489. He is crucial to the development of Luffy's character and the overall narrative of the series.