The Cousins are the Prince's cousins. Since Katamari Damacy, the series has introduced more and more cousins every game. In canon Katamari games, the grand total is 58 cousins (57 excluding The Prince).
In We ♥ Katamari, the player can see the life of the King of All Cosmos from childhood to adulthood, however, the cutscenes never portrayed, or even hinted, that the King has brothers and sisters, neither that Papa has other offsprings. This may imply that, either The Queen of All Cosmos had siblings that gave birth to most (if not, all) of the cousins, or that maybe the King has other family members that the games haven’t acknowledged yet.
Katamari Damacy has 23 cousins, 24 including the Prince. You have to complete the game to unlock them
- The Prince
We Love Katamari added 16 new cousins. They are called second cousins. The first cousins, in one way or another changed their looks and features in this title as well (such as Velvet gaining artificial legs and Jungle blending in with the background).
Me & My Katamari added 8 new cousins. They are called rookies.
Katamari Forever - ???
Katamari Forever added 2 new cousins. The title of these new cousins was never revealed. These cousins also have different names in Japanese. The Japanese names are in parenthesis.
Katamari Damacy Online, a Korean game by Windysoft released their own set of cousins. The game isn't available outside of Korea. The more commonly known cousins outside of Korea are Mint, Melo, and Wink. There is also an unnamed katamari cousin that represents the player in the dating sim Namco High II. Three cousins were introduced in the Katamari web comic: Toothy, Bandaideo, and Crif.