What do you want to know?

I have two questions, both actually originating from the same passages in An Artifical Night. (And either or both of these may be more appropriate as FAQ-type questions, I just don't have a good way to know how involved the answers would be.)

The first is, how relevant really is the existence of "royal" members of the Cait Sidhe, if they determine the ruler by combat? I had assumed there was no real royal family until Tybalt made such a big deal of Raj being the only younger royal there was and Toby seemed to assume that Raj would one day replace Tybalt. Or is it just that only royals can fight for the right to rule? (also, the assumption that Tybalt will be replaced seems odd to me, just in that if he's immortal, he should theoretically grow stronger, not weaken with age)

The second question is about the use of the word "pureblood". In Rosemary and Rue, I got the impression that that just referred to people with entirely fae, and no human ancestry. But some of the useages in An Artifical Night made me think it was also (or possibly, rather) used to delineate purity of species, ie, Raj's heritage is entirely Cait Sidhe with no other kind of fae involved. So I guess I was just wondering if you could say more about how that term is used, and how inheritance of "species" of fae worked in the case of cross-species pairings?