CLOSE RELATIVES: None.
SKILLS AND ATTACKS: Invincible.
BACKGROUND: Urchins chose to not join the Koopa Troop and to keep their peaceful lives in the ocean. It's not their fault that Mario and friends keep bothering them. They've been sighted in waters surrounding Dinosaur Land, Vibe Island, and in the Beach Bowl Galaxy showing that they get around one way or another.
EVOLUTION: They've appeared pretty much the same in all of the games that they have been in. Super Mario Galaxy is the first game that they've appeared in 3D.