I know that everyone's saying that Guillermo can't be turned because he's got vampire hunter blood, but I think that there's a funnier option:
What if he's spent so much time being a familiar surrounded by vampires that he's just become immune? Like with the hypnotism? Familiars generally don't last as long as him so there's no frame of reference. It would be so ironic for him to have waited so long to become a vampire only to find out that it was the waiting that ruined it for him
Guillermo isnt Human or Vampire but a secret (cooler) third thing is honestly the best option for us
If I were Guillermo and had a stressful coming out and no one gave a fuck and I saw my vampire friends throwing a pride parade after the neighbor comes out I would be at my limit I would slay them all
