From the Super Mario Wiki
The Noki grandson is a Noki in Super Mario Sunshine. He resides in Noki Bay along with his grandfather. Whenever Mario and F.L.U.D.D. arrive at Noki Bay, this young Noki is usually found near the beginning of the level. He tells Mario where to find his grandfather and gives him a helmet for an increased air supply in water in certain missions. He also has a wife and a child, as seen in Noki Bay's Episode 8. If Mario talks to him at the beginning of this Episode, he tells him that he retrieved them from their hiding place after the pollution in Noki Bay disappeared.
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