Theory: Motley Bossblob is a Member of Bowser's Species

Arguments

 * Argument 1: Motley Bossblob in his standard form resembles the Koopalings & Bowser Jr. He particularly bears a strong resemblance to Larry Koopa with his muzzle, which features two downward-pointing fangs, as well as his yellow skin and claws. His height is similar to the heights of the Koopalings. His eye shape, hands and feet are near-identical to those of the Koopalings and he also has two golden bracelets on his wrists, much like how the rest of Bowser’s Species have black, spiked bracelets.


 * Argument 2: His magic wand is identical to the wands of the Koopalings, albeit his wand’s jewel is pink, a colour that matches none of the other wand’s Jewels.

Picture comparison of Motley Bossblob and Larry Koopa: