And then I remembered that I had had a cousin inherit a kingdom from a queen after she had managed to offend one fairy tale hero too much so he went off and married a miller's daughter and left her with her nose entirely too long for any man to consent to marry, especially after refusing all sorts of suitors first. And I wanted the cousin poor.
Wrestling and wrestling with the notion -- would have to be a descendant from her royal side -- what could I do to make the sibling up the tree not inherit -- obviously if the two older brothers were disinherited for trying to murder the youngest, they would never get it, or their descendants -- and if they went off to seek their fortunes they would have kingdoms because they would marry royalty --
Well, duh, it finally occurred to me that he could have a kingdom. A small and poor one if that proved necessary.
I also thought of the "she asked a monarch most closely related to her for one of his sons as her heir", which does have some fairy tale provenance ("The Bee and the Orange Tree") even if literary, but then, that would require a somewhat less arrogant princess.