Maybe a bug or a mod issue on my end but new Traitor Kings are not spawning as options for recruitment. Three showed up originally but I ended up losing one in a battle as he wasn't immortal yet. After Hiring another the third disappeared. So other than the generic you get during the ascension quest I don't have any more to hire.

I am going to play around with my mods as I do believe I had a single one that effected Lord/Hero spawn rates that might have been the issue and try a fresh start from that, if that doesn't work, or if I'm misunderstanding something about the Traitor Kings let me know.