YouTube Kids launched in 2015, as a portal for child-appropriate content with parental controls. It has been over two years since then, but for most of that time, only apps for Android and iOS were available. An app for select smart TVs was released in April, and now Android TV owners can use the service as well.
Judging from the screenshots, this appears to be the same exact app released for smart TVs. Considering the main YouTube app has been switched to a web wrapper, it seems likely this is one as well. Like the mobile app, YouTube Kids TV is split into four categories – shows, music, learning, and explore. Features requiring you to login, like content blocking and YouTube Red, are not available on this app yet.
YouTube Kids TV appears to be compatible with all Android TV devices, and you can grab it from the Play Store below. You can also download it from APKMirror.