If you unlink them they'll become individuals (like, say, Baldur's Gate II).
Also nice to see a more storycentered gamer rather than the mechanical ones I often see on this forum, not enough of us.
Also, haven't had any companions initiate dialog with me regarding their plot stories, maybe I'm just not far enough. But I would've thought Selene and the Prince would be contentious.
Not in the game yet (try talking to them and you see the WIP-dialogue).