This photo of adorable (and incredibly rare) biracial twins is going viral

Adorable 9-month-old fraternal twins from Illinois are getting lots of attention on Facebook—and it’s all because their mother posted side-by-side photos of them dressed in identical outfits. The twins are biracial, a fact that their mom proudly points out.

“We're chromosome twins,” Whitney Meyers wrote in a Facebook post that’s gone viral. “Kalani (on left) is light with blue eyes and Jarani (on right) is the darker one with brown eyes. This is rare but so awesome to share.”

Whitney is Caucasian while her partner, Tomas Dean, is African-American. Whitney posted another photo on Facebook pointing out that it’s “really odd and neat” that her twins are biracial.

Whitney’s right: This is rare, but it happens. According to the BBC, a biracial couple who are expecting twins has about a one in 500 chance for the babies to have different skin colors.

Whitney tells ABC affiliate KHQA that she was blown away when she first saw her babies. “At first when they were born, I wanted to believe it, but it’s so rare I didn’t think it’d happen to my twins!” she said. “But sure enough, they’re biracial twins!”

Whitney says the twins also have different personalities: Kalani has a lot of energy and is already crawling, while Jarani loves to eat and hasn’t started crawling yet.