Was pondering it after Poul Anderson's "Time Lag" -- which does indeed have a nobility, but the man's title is Freeholder. The planet's chief of state is a President, though it doesn't go into whether he's elected or hereditary, and I suspect even if it's elected it may be among the Freeholders, or perhaps even by the Freeholders rather than by average citizen. "Elector" was not a high-ranking title in Europe for no reason. Which is rather more likely for far future. "Prince" is itself after all merely a descendent of Augustus Caesar's euphemistic First Citizen.
Hmm. . . hmm. . . nevertheless I have a princess. The title was settled on her ancestor Somebody the Wise when they were belligerently defying another planet, a People's Republic, and its unsubtle efforts to subvert them -- they take the charge that they are effectively a monarchy and decide they shall be a principality instead. Perhaps Somebody was not wise enough to tell them more than he refused to be king; perhaps he said that he would accept any form of government they propounded as long as it did not make him king. Come to think of it, I can make that a legend that I do not confirm or deny within the story, as soon as I find a place to slither the knowledge in. . . .
It's easier when you accept a translation convention that everything's been rendered into modern English, no doubt. But this is fun.