You hear about them everyday in the news because of the allegations of cheating, by both of them.
My wife has been saying that Kate is Choleric, and John is Melancholy, because he doesn't really want to be bothered with all the attention. I have never paid attention to the show, so I do not know. I assumed they were discussed here sometime, and looked for it, but it looks like they weren't
So what type are they?
If Kate appears Choleric on the surface like that, that would probably suggest an In Charge type (EST/ENJ), and if John is Melancholy, he's probably Chart the Course (IST/INJ).