I have a huge birthmark that is red that covers my right shoulder, and no one else in my family has EVER had one. It's really strange... I used to hate it, but now I LOVE it! Why do you ask? Does your baby have one? With my first baby my mom said she had dreams that my baby would have a birthmark on her face, and that is the first thing she looked at as she was coming out! lol! It really freaked her out. But I think they just make you extra unique!!