UK (BBN)-Thanks to a rare quirk of nature, Lucy is the alabaster-skinned redhead, and Maria has their part-Jamaican mother's dark skin and hair.
Images of the Aylmer sisters of Gloucester, United Kingdom, rocketed around the Internet this week when a British newspaper carried their story, reports CNN.
"I can't stop crying! This is all so amazing," Lucy Aylmer posted on Facebook.
The girls were born to a white father and a biracial mom in 1997, according to the Daily Mail story that started all the fuss.
'No one ever believes we are twins," the newspaper quoted Lucy Aylmer as saying.
"Even when we dress alike, we still don't look like sisters, let alone twins."
Appearing Tuesday on "Good Morning Britain," the sisters said they're always facing doubters who can't believe they are related, much less twin sisters.
Some even asked whether Lucy was adopted, she told the show.
"It was pretty hard," she said.
"It went on in secondary school as well, and it wasn't very nice."
Maria said they've been told the chances of such an occurrence are "one in a million."
The BBC, reporting on a similar case in 2011, said it was more like 1 in 500.
No matter the odds, the sisters say they're happy with how they look.
"Maria loves telling people at college that she has a white twin -- and I'm very proud of having a black twin," Lucy told the Daily Mail.
"My family is beautiful," she posted on Facebook.
BBN/SK/AD-07Mar1:40pm (BST)