my younger brother was like that. He was actually incredibly good at it and still is, but just doesn't do it too much anymore.
My town has the largest children's circus in New England - Gym Dandies - that almost everyone in my town was in at at least one point or another. I was in it for maybe 2 months. Anyways, everyone learns to ride a unicycle and some kids get really good at it and buy their own better unicycles - my brother being one of the few.