The Royal Cousins in We ♥ Katamari.
Cousin Stage Where in the stage
Ace Tutorial stage You need to roll him to finish the tutorial. He rolls a ball on the outer edge.
Slip Tutorial stage Replay the level as Ace, and you'll have to roll up Slip instead.
Macho As Large/Fast As Possible 1 Riding a crawfish around the seated person.
Can Can As Large As Possible 2 On the table in the house.
Havanna As Large/Fast As Possible 2 Sitting at the picnic. You need to have rolled up Can Can.
Johnson As Large As Possible 3 On top of the Daruma pile by the table in the apartment.
Twinkle As Large/Fast As Possible 3 On top of an Xmas Tree in the yard just in front of the 50cm barrier.
Kuro As Fast As Possible 3 In the schoolyard, flying under the hurdles. You need to have rolled up Twinkle.
Foomin As Large As Possible 4 In the park, just past the stairs up on the apartment complex side.
Miki As Large As Possible 4 Waiting in a line for the fortune teller in the first town. You need to have rolled up Foomin.
Velvet As Large As Possible 4 Riding on a shark next to the beach in the town after the 3m barrier. You need to have rolled up Miki.
Shikao As Large As Possible 5 Watching TV near the pandas in the first town.
Lucha As Large/Fast As Possible 5 On the top of a stairway of wrestling mats in the second town. You need to have rolled up Shikao.
Nutsuo As Large/Fast As Possible 5 Riding a dinosaur at the base of Niagra Falls. You need to have rolled up Shikao and Lucha.
Drooby As Large/Fast As Possible 5 Drilling an oasis in Egypt. You need to rolled up gotten Shikao, Lucha and Nutso.
Marny Underwater Stage Riding a manta ray near the car the second time you play this level.
Odeko Race Stage Rolling a katamari around the road in the middle part of the stage.
Shy Race stage In the same place as Odeko.
Nickel Race stage In the same place as Shy and Odeko.
Lalala Snowman stage She's under an umbrella, you need to be quite small to get her.
Nik Sumo stages He's on a stage in a park, next to some plates. You need to be bigger than you'd expect.
Fujio Cloud stage On Mt. Fuji.
Marcy Saturn Small On the toy robot's shoulders. Dash off the corner of the bed to get her, or roll a katamari big enough to get her normally (you'll be around 20cm).
Peso Saturn Medium Lounging by the kotatsu in the supply room.
Signolo Saturn Large He's running around the streets in "New York" (or France--he can be found very near L'Arch de Triomphe).
Honey Sweets Stage On the hillside next to the house.
June Cloud stage Playing jumprope between two cloudmen.
Ichigo Flower stage At the start, riding a deer.
Dipp Firefly stage On top of the central hill.
Opeo Origami Stage On a bed in the corner of the bathroom.
Jungle Baby stage Riding a coelecanth in the jungle/swamp part.
Miso School stage On the desk nearest to the blackboard.
Kinoko Campfire stage Dancing around a lit campfire with old people.
L'Amour Tidy-up stage Walking/standing around in the middle of the room.
Daisy Cow-bear stage Running around at the head of a line of cow/bear-men. She counts as a cow and will end the stage.
Huey School stage With the younger students after having collected Miso or during the time trial version.
Beyond Zoo stage 1 On top of the hill next to the swamp.
Colombo Zoo stage 2 Riding an alligator in the swamp.
Odeon Money-raising stage He's in the school yard, at a stall next to the entrance gate.

Note: You can get one new cousin per stage, that's why you need to get certain cousins before others. After you get the needed cousin, come back and the new cousin will appear as well.