@Turjan - Bingo, we have a winner! (and yes sorry, I am almost positive your name is not "Bingo")
The Harpy is "Mean Girls" style female bully gang, that puts down local sims and generally only think about themselves.
On City Hall or an in-game computer,
NRaas > SP > General Options > Options: Personalities > Options: Town Harpy > Weight: Impress > (try changing this from 10 to 0).
"The relative chance the leader will pass down a trait to one of the members."
Alternatively, if you like the effect you could use SP > Sim (Household, Caste) Options to exempt certain sims from being members of this clan. Or if you don't like the personality to begin with, though what's not to like about "Mean Girls" as they are just so lovable, you could switch off its progression from the Options: Town Harpy menu above and then I believe the clan will dissolve. Or at least stop doing stuff to the town's sims.
Note that there is a similar function/option involving trait switching on the Town Thug from the same module.
Edit: It should also be noted that all of the SP Personalities and their effects are really best to be disallowed on a Rotational caste, although this just becomes a matter of personal preference. Only inactive sims can hold clan membership or leadership anyway, so once you return to the household to play the sims who have picked up personality positions, they will lose them immediately.
NRaas > SP > Caste Options > Rotations (or whatever you are using here) > Personality: Allow > False