From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Planet Kaishin (界芯 惑星, Kaishin Wakusei; FUNimation "Planet of the Kai", Viz "Kaioshin's faraway planet"; Literally meaning "World Core Planet") is a planet.
Planet Kaishin was the original homeworld of all Kaios, Makaios, Kaioshins, and Makaioshins. The planet was described in the Dragon Ball: Sūpā Ekisaitingu Gaido as a "large version of a Kai Planet" (something like a big version of Grand Kaio's World). On the planet, there were gigantic trees called Kaiju. These trees sprouted beings named Shin from the magical fruits it grew. These Shins could later possibly take the role of a Kaio if incredibly lucky, or if born from special golden fruit then they could become Kaioshins. Evil Shins, known as Makaios and Makaioshins, were cast into the Demon Realm to be kept separate from civilization. The population of this planet was roughly 80.
Note: All Shins shown in the series were all Kaios at the time of their appearances, thus all had left their homeworld ages ago.