Pumpkin Pirates

The Pumpkin Pirates were a group of children who pretended to be pirates that lived on Ruluka island 50 years ago. The members are Rapanui Pasqua, Isoka, Henzo, Pukau, Longo and Akibi. One day, their home village was attacked by Whetton and his pirate crew. The Pumpkin Pirates managed to foil the pirate's plan, but only to be sucked in the Rainbow Mist and ending up in Ape's Concert. Only Henzo managed to escape, sacrificing himself to save his friends from Whetton. The rest of the Pumpkin Pirates have been living in Ape's Concert ever since and managed to survive. Until they meet up with Luffy, Zoro, Usopp, Robin and a grown-up Henzo in which they help them stop Whetton's scheme and were returned home earlier on in the timeline. In an Ontological Paradox, they become the very Marines that chased the Straw Hat Pirates to Ruluka island in the first place.

Trivia

 * Rapanui is the only member that has a surname. He also is the only one to have a known rank, being a lieutenant commander.
 * All of them became Marines except for Henzo who became a scientist.
 * They became Marines during the times when pirate legends such as Roger and Whitebeard were just rookies, making them some of the oldest known Marine veterans.