I'm pretty sure "Koopa Kid" and Bowser Jr. are the same thing. What's the difference? And by the way, Koopa Kid is a playable character in Mario Party games, for those of you who didn't know.
But just in case I'm wrong about them being the same person(Which I'm not), there would then be the 7 original Koopalings, plus Bowser Jr. plus "Koopa Kid", plus the Koopa Kid Trio in Mario Party....Holy! Bowser has 13 kids!