I'm in the process of reinstalling my TS2 game, wow, forgot how long THAT takes. Anyways, there is something I can't remember about the TS2 vampires. I do know that if your sim gets a little too friendly with the Count or Contessa, this will kick in them turning other sims, and they will for sure turn your human sims that befriended them.
Now my question is will your vampires that were once human, but not the Count or Contessa. Will, they automatically turn another sim, or is this something that is completely left up to the player to do?