Can I make my Sim a descendant of Guidry?

I suspect that he and Temperance (his angry ex-)  aren't regular sims because when my magic user sim learned the "dedeathify" spell that allows ghosts to be magically resurrected as human living sims I tried the spell on both of them and ... well, the spell didn't even appear in my pie chart of spells available.   So they apparently are hard-wired to be ghosts and nothing else?  I love being able to to turn ghosts back into playable sims though.  I thought about making that sim into a reaper but I don't like taking sims away.  I am afraid nobody would die in my neighborhood if I was playing as the Reaper.