Kabumpo, the Elegant Elephant of Oz, is primarily a subject of the Kingdom of Pumperdink. In fact, he is an honorary Prince and Chancellor of the Realm, and advises King Pompus on everything from foreign policy to when to get a haircut. He has, however, formed links with many other monarchies during his travels. He visits the Emerald City enough to be a part of Ozma’s court as well, and John R. Neill seemed to have the idea that he lived there. In fact, he’s not only always in the capital but accompanied by Ojo, another oddity on which I’ll have more later.
During the events of The Purple Prince of Oz, Kabumpo takes a wandering mountain boy as his attendant, and the boy turns out to be Prince Randy of Regalia.
While he never becomes part of the court of Regalia, it does appear that he visits there quite a bit after that. Again, this appears to have confused a later author, with March Laumer’s Frogman stating that the elephant lives in Regalia. In Purple Prince, he also befriends the Red Jinn, a ruler in his own right. I don’t think any of this lessens his loyalty to Pumperdink, but it might well lead to alliances between that small country and others. Returning to the Neill books and Kabumpo’s partnership with Ojo, we have to remember that the Munchkin boy also shouldn’t be living in the Emerald City if we’re to go with how Ruth Plumly Thompson left him. In Ojo, he’s revealed to be the Prince of Seebania, and moves there with his newly restored family. This actually suggests a possible explanation, however. If one of Kabumpo’s attendants was revealed to be a prince, maybe he took on other princely assistants after that, including the Prince of Seebania.
It would be a good way for him to establish ties with more parts of Oz, after all, and for the princes themselves to gain a certain amount of prestige. Kabumpo is, after all, a celebrity known throughout Oz.