Ace

Ace is a cousin of the Prince, known for pretty much nothing special. He holds a grudge against his more popular cousin, and seeks to disrupt him as much as possible. Usually though, the King catches Ace in the act and ends up punishing him publicly. Despite this, Ace never gives up his goal of annoying Prince. He makes a deal with Maxwell in Episode 2, that if he revealed the location of the Crossover Avengers base, they would give Ace pretty much everything Prince owns. This deal has yet to be fulfilled by the villains though.

Abilities
Like his cousin Prince, Ace is capable of rolling around katamaris the same way Prince does. He can also use related powers like Charge-N-Roll and Miracle Eye, but can't use Royal Family powers like Prince Hop or King Shock. To compensate, Ace is much zippier (faster) than Prince, has more stamina, and can control his Charge-N-Roll better.

Personality
Ace is a rambunctious, energetic, and mischievous cousin of the Prince. He feels overshadowed by his far more popular cousin, and harbors a deep jealousy towards him. Ace decided to go rogue, and attempt to unseat Prince's position of popularity by interfering as much as possible with him. He isn't 'evil', but more of a persistent troublemaker.