Piccolo is initially assumed to, like his parent, be a member of the Demon Clan (魔族, Mazoku), however, midway through the series it is learned that they are actually members of the alien race called Namekians (ナメック星人, Namekku-seijin).

Is Piccolo Piccolo a demon king?

Knowing that he would only be accepted for the role if his heart was pure, the Namekian split himself into two beings: his good half, Kami, and his evil half that would later become the great demon king, Piccolo. ... Thanks to his usage of the Pokopen ability, King Piccolo was able to "reincarnate" himself as Piccolo Jr.

How did King Piccolo become evil?

Young King Piccolo in one of Master Roshi's flashback. Kami and Piccolo Daimaouh were once the same being, the Nameless Namek, but when he wanted to become Guardian of Earth, he had too much evil in his heart, so he expelled that evil, dividing him into two, the good half, Kami, and the bad half, Piccolo Daimao.