StoryProgression 267: SP likes to make the leader of either Pack or Feral also be the Hound.

However, it doesn't seem to stick, because the creation message pops up at least once per sim day, and I never see any other messages about Hound activities. Checking either the sim's tooltip or status with MC shows that they are, indeed, leader of both clans. Manually reassigning leadership does no good; it's undone the next time SP checks for a Hound candidate.

I can temporarily stop it by going into the options for the sim in question, SP > Sim Options > Personality > Personality: Disallow > Hound. Eventually, of course, that sim will die (probably at the hand of a Helsing) and another one will try to take up both torches.

This is just off the top of my head, and keeping in mind that I don't play around with some of these SP personalities very much. But can you not define an Automatic Caste using clan membership as criteria (Caste Options > Caste:Personality Leader/Member) while disallowing its resulting members from becoming or allowing to remain Hounds (Caste Options > Personality:Disallow)?

That sounds like it should work, and I'll try it. However, it's not ideal -- a Pack leader, for example, should be allowed to be a member of Hound if they fit the criteria. My towns tend to not have many werewolves (I think the scenario for having werewolves spread the curse doesn't work or never runs) so I would not mind membership in multiple clans. This would only block leaders from joining though, so not too bad.