I've 'run into' (read: mercilessly slaughtered and looted) them a few times, too. I always assumed there'd be a questline connecting to them if you were a Vampire or something, but I never got around to vampirism.
According to the UESP wiki there's no quests relating to them, which is a shame.
Also, wierdly enough, apparently if you hit them with Healing Hands there's a chance they will become hostile. Maybe they think it's some undead trickery...