My sim (who was born a fairy) had a baby with a vampire, and their son has both the vampire and fairy hidden traits, has the vampire glow, and fairy wings, moodlets and CAS classification. He's still a toddler so I'll have to wait to see the extent of his vampiric powers. I'll try and take screenshots, but has anyone ever encountered this kind of hybrid?
Oh, and in the relationship screen, instead of a green box (fairy) or pink box (vamp) his box is red. O.o I wish I knew more