We use Zelazny's essay from The Black Road War as our reference for parentage.
A Note on Titles
While each child of Oberon carries the title of prince, they also have an array of other, 'junk' titles. Some of these have small amounts of land or resources that go with them, but mostly these are just nominal honorifics handed out at some point when Oberon was pleased with something, or when he wanted to play the siblings off one another. Features can take a pretty free hand with these titles, so long as they stay primarily color.
Regencies are the exception to this. Amber has only a small number of regencies, and their assignment is a significant honor, since it puts the regent in charge of a Golden Circle shadow. Two regencies of note are Weirmonken and Ghenesh, held by Eric and Corwin.