Things like this kept on happening to me when I first got Vampires for i.e., my very first playthrough. I had spent a significant amount of time designed my family in CAS and thinking up a (vague) backstory. One of the 2 Young Adults was a Vampire, the other (his wife) was a Human and his Adult mother (who also lived with the family) was an Alien. Cue Caleb Vatore coming over to welcome us, me forgetting that my male sim was a Vampire, leaving him outside to socialise and focusing more on the female sims when I suddenly hear the music of Doom and frantically click on my male sim just in time to see him perishing in the daylight as the sun rose :'(