Vampires cannot turn younger Sims—that just wouldn’t be right to steal life away from children and teenagers before they are able to make such a momentous decision on their own.
Besides, feeding on a little kid? That’s just creepy-wrong. Yet there can be vampire children...sort of. It just happens by traditional means.
A vampire may become romantically involved with either another vampire or a normal Sim. After successfully Trying for Baby, two vampires produce a child with the hidden Vampire trait.
When that child becomes a Young Adult, they automatically become a full vampire without the growing pains other Sims experience during the turning process. If a vampire and normal Sim create a baby, there is only a 50 percent chance it carries that hidden Vampire trait.
Though younger vampires do not Drink, Hunt, or Read Minds like fully developed vampires, they still exhibit a few of the physical vampire traits just to let you know what’s coming. Look for pale skin or reflective eyes.