Well, Pratchett has the good true heir, Carrot, who recognizes that the city is better off under the pragmatic..."usurper," Vetinari. But he also has the true heir who doesn't want to be king (Tomjon), and the sort-of-heir/usurper who turns out to be quite good at it (Verence) in Wyrd Sisters. Not exactly the thing, but I'll keep thinking.