'They bring people together.' Twins with different skin tones celebrate 1st birthday

QUINCY, Ill. -- Two unique twin sisters just celebrated their first birthday!

Bi-racial twins Kalani and Jerani were born with two completely different complexions and instantly became social superstars. The girls celebrated their first birthday on Sunday with a princess-themed party.

Their mom, Whitney Meyer, posted a picture of the girl's cake on Facebook. The cake was a custom princess marble cake with cake toppers to reflect each sister.

But how did twins who are fraternal come out with two different complexions?

Dr. Angela Bianco of Mount Sinai Hospital says skin color is determined by multiple genes, but fraternal twins come from two separate eggs, and two different sperm.

"By virtue of chance, one twin can inherit more DNA from a specific parent in contract to its co-twin, and that DNA can code or translate for things like skin color and eye color," Bianco said.

The girls are getting lots of love and a caring embrace from people around the world.

"I'm so happy about that," Meyer told People. "You get some people who will say some stuff, but mostly everybody loves their uniqueness. I hope I can bring different people together."