In monarchies and feudal societies the line of succession was extremely important, having an heir was one of the primary goals and creating familial connections was important to creating alliances. In a world where there are multiple races, and none of them can interbreed, what type of systems would arise?
Because of the importance of marriage alliances and lineage in medieval-style monarchies, would it be possible to have these separate races (again non-interfertile) share some amount of power within the kingdom? I can't really think what systems would stop one race from trying to dominate the others, and that most races wouldn't accept a king/queen that isn't of their race (probably because of racism, but also that it limits how far they can rise within a feudal system).
I do think having races (or at least certain cultures within the race) accepting rule under a different species isn't unbelievable. Obviously there tend to be minorities in all sorts of kingdoms (Roma, Jews etc.). As well, I understand that there are likely to be at least a few countries that attempt to keep a fairly mono-race attitude. But I don't want every kingdom to have to be black and white where a species is either the ruling species of their country or they are an oppressed group within the kingdom.
As an example, in Brian Jaqcues world of Redwall, there are many races that live together but the only 'Kingdoms' seen are all pretty mono-species. None of the species are interfertile and I was trying to think of a way that a kingdom of say mice, rabbits and squirrels could exist without one species being completely dominant. Anywhere shown to be fairly multi-racial tends to either be very small in scale (Redwall itself) or are hordes of 'vermin' where they have no real structure besides might is right.
Would it be possible to have a multi-raced feudal kingdom where there isn't a singular dominant race, and if it is, what systems could ensure that any race can not only rule as a lord but has a chance of putting their line on a throne?