Biracial twins look wildly different

If a stranger happened to meet 18-year-olds Lucy and Maria Aylmer on the street, they'd likely suspect they were close friends, but probably not sisters.

But they young women aren't just sisters: they're twins.

Lucy and Maria are fraternal twins born to a Caucasian father and a half-Jamaican mother, according to World Wide Features. Lucy ended up with pale skin with red hair, while her sister Maria has much darker skin and curly black hair.

Growing up in the UK, even their friends didn't believe they were twins. Some even asked them to show them their birth certificate.

Fraternal twins develop from two different eggs by two different sperm -- so they can often look slightly different. Although some, like Mary Kate and Ashley Olsen, end up looking so much alike they're mistaken for identical twins. According to the BBC, there is a one in 500 chance fraternal twins will have different skin colors if they're born to a interracial couple.

"Now we have grown older, even though we still look so different, the bond between us is much stronger," Lucy said. "Now we are proud of the fact that we are each other's twin sister. Maria loves telling people at college that she has a white twin - and I'm very proud of having a black twin."