Haru-ōji

The Prince Haru is the prince of the Mushroom Kingdom. He appears in the anime movie: "The Great Mission to Save Princess Peach".

He first appears in the begining of the movie as a blue dog named Kibidango who has been turned into a dog by King Bowser. At the end, thanks to Mario and Luigi, the prince is turned back into a human.

The prince is most likely Princess Peach's brother. He has never appeared in any Mario game, or even been mentioned. Plus, Peach has never mentinoed a brother in the games, and probably doesn't even have one.