Momotaro is the reincarnation of Kohaku of InuyashaJust take a look at both characters. They both have dark brown spiky hair held in a pony tail. They are also known for slaying the demons (mostly zombie ones in this Momotaro's case). So perhaps when Kohaku died, he was reincarnated as the next peach boy.
Prince Charming is somehow related to the King of the Cosmos from Katamari DamacyBoth characters have grey skin and are known for being camp gay among their series' fans. It's worthy to note that Prince Charming is significantly larger than the rest of the cast.