They are actually not genies, even if even commentators in VGC tournaments call them like that -_- They are Japanese kami, Tornadus is the divinity Fûjin, while Thundurus is Raijin. It is weird that pokémon that Japanese were first introduced in Unova, but then in Legends Arceus we got to confirm that they are indeed avatars of nature representing each of the four stations, with Enamorus being the one for spring, and Cogita tells the player that even when they spend a lot of time in Hisui (currently Sinnô), which is based in Hokkaidô, Japan, they like to roam the entire world, and that explains their presense in Unova.