Complex sentence: There are two known ice giants in the Solar System, Uranus and Neptune, although there has been recent substantial evidence of a third ice giant, tentatively nicknamed "Planet Nine", as it would be the solar system's ninth major planet.
Split into simpler sentences: There are two known ice giants in the Solar System, Uranus and Neptune. Recently, substantial evidence has indicated the existence of a third ice giant tentatively nicknamed "Planet Nine", as it would be the solar system's ninth major planet.