How Twins Work

African-American teenage twins
Twins are unique people who are also eerily similar to each other. Big Cheese Photo/Getty Images

I walk into a restaurant with my family. The heads start to turn. People walking past do double takes, and I'm thinking, "Why did I have to wear a black dress, too?" Finally, after we're seated, the question comes from the wide-eyed waitress: "Are the two of you sisters — I mean, twin sisters?" Invariably, more questions follow: "I always wanted a twin. What was it like? Did you always dress in matching outfits? I bet it was fun. Did you play jokes on people? Trick your parents, teachers — maybe even a date or two? What about ESP — do you always know what your twin is thinking?" I can pretty much tell what she's thinking right now, because it's the same as me: "Why do people find twins so fascinating? And, thank goodness we're not triplets!"

Whatever the reason, there's no denying that people have been, are, and probably always will be fascinated by twins and other multiples. And the numbers of twins seems to be on the rise. But what's the reason for that? What causes a woman to conceive twins and why are some identical while others are fraternal?


In this article, we'll look at how twinning happens, whom it's most likely to happen to and what types of twins are out there. We'll also tackle some of the interesting topics that surround twins — like ESP, twin languages and more.