The King is the current ruler of space, often refered to as the Cosmos. He came to power when his father retired as the previous king. He married the Queen and had his first child, the Prince. Sometime after his son was born, he invented the Katamari and the game associated with it, Katamari Damacy.
The Queen met the King when they were both teenagers. She is apparently very talented, skilled in music, art, and horseback riding. She is a very sweet woman, but even the King is cautious to anger her. She seems to love Katamari Damacy as much, if not more than, the King. The Queen does not appear to speak in any of the games, but she leaves the player a message at the end of We ♥ Katamari depending on how many Fans and Cousins the King is able to roll up during the credits.
The first child and only son of the King and Queen, the Prince is the main protagonist of the Katamari games. He is tasked by his father to roll objects into the Katamari to create stars, planets, or islands, depending on the setting of the game. While this may seem like hard work, he does not seem to mind. He is hard working and dependable, and willing to take on the tasks the King assigns him.
The King's father, called only Papa by the King, is the former King of All Cosmos. He was once a tough and bitter man who wished only to mold his son into a champion, but has since come to be more accepting of his son's dreams. He once entered the King into a boxing contest, where the King placed second, and in disgust threw away the trophy. He also objected to the King having a girlfriend, which escelated into a fist fight, but Papa stopped and walked off. It was when the King saw Papa in his room, looking at the trophy that had been thrown away, that they made up, and when Papa crowned the King as the new ruler of the Cosmos. He was introduced only in cut scenes in We ♥ Katamari, but can be rolled up in Beautiful Katamari, and Me and My Katamari. Papa is the one in the middle in the picture.