albino... maybe? he does have the white hair / red eyes combo after all though as you said to me it's more a design choice in order to be reminiscent of manga kitaro. but it makes sense to think of him as albino... as for the status of the yuureizoku, I admit I don't really buy it - characterization differs from one media to another, but even in general from the way they are described, and gegero's demeanor, speech, values, humility etc I don't get a royal vibe from him at all quite the contrary haha.

yokai are consistently characterized by the fact they don't live by the rules of exploitation and capitalism of humans ; it's the root of many problems kitaro has to solve even. so even if yuureizoku seem to have a certain reputation amongst yokai i don't think it has to do with any concept of nobility. especially with genazo - the whole story is about how not only the yuureizoku character rejects concepts of exploitation, power and influence, but his people are direct victims of those. stuff like "valueing the purity of the bloodline" imo does not go well with gegero's character at all given the contents of the movie...
it's true that medama oyaji is portrayed as being proud of his people, and early medama could be pretty vocal and even harsh to kitaro about it. again, different media, different characterization ; but i do think in genazo he keeps that pride and respect for his ancestors, but given the context of his people being written as, well, literally an ethnic minority being genocided by the urakido before the ryuga started exploiting their literal blood ; that his people are important to him makes a lot of sense and it's a story i value a lot more than royalty i guess.
but hey! its what fanfics are for B)