TIL Pluto has moons other than Charon. Astronomy is one of my strong suits, but even then that was new...
New discoveries are made all the time, you just happened to have outdated information since the other ones were only discovered this millennium. Though I'm a proponent of classifying Pluto and Charon as double dwarf planets instead of Charon just being a very large moon relative to Pluto.
Seconded. When the satellite is half the size of the planet, it's barely a satellite any more...
Some astronomers think that even the Earth and the Moon should be classified as a double-planet system, because the Moon is a sizable fraction of the Earth's size, while almost all other satellites in the solar system (except Charon) are minuscule, compared to their parent planet.