The secret society members in my neighbourhood don't age for some reason, probably because of Pescado's mod. Anyway, can I make them into vampires? It would make better sense that they are since they don't age. I am not using cheats to make them vampire, I am going to influence the dad of my current sim who I turned into a vampire so he doesn't die to bite their necks.

No townies age unless you make them. SS members aren't unique.

They're just ordinary dormies, so you can do whatever you want with them.