March 2021
I had this problem now too, twice from the same human father with different human mothers, both where NPC woman, living in no house.
Both kids were born in Evergreen Habor. The one thing that could have happened to both is that they were made in the dumpster?
July 2021
I had twin vampire boys born to human sims in Newcrest who had the house trait "On a Dark Leyline" during the pregnancy, she had the buff "Hoping for vampire babies."
Think this may be unintended.
July 2023
Similar thing just happened to me. Two human parents with 0 vampire relatives gave birth to a vampire baby. There are no lot traits and there have never been vampires living on that lot. Both parents have had their plasma drank by vampires multiple times in the past and mom has woohooed with a vampire multiple times, but that was a long time ago and the dad is 100% her human husband. I'm honestly at a loss as to what I'm supposed to do with this plot-wise.