Kate Middleton
Kate Middleton is often compared to Pictured: Middleton takes part in preparations for a Commonwealth Big Lunch at St Luke's Community Centre on March 22, 2018 in London. Getty Images/Paul Edwards

Kate Middleton shares some similarities with another royal, Princess Mary Elizabeth Donaldson.

According to Amalie Henden, a journalist for Express, the Duchess of Cambridge is often compared to the Crown Princess Mary of Denmark. The two have long, dark hair and pale complexions. In addition, they both came from "normal households" before joining their respective royal families.

Designer Karl Lagerfeld dubbed Middleton and Donaldson as the "Royal Sisters." He also pointed out the two women's similar styles.

Donaldson met Prince Frederik of Denmark in a pub named Slip Inn in 2000. According to her, their encounter was "completely random." She reportedly went to the pub to meet some of the Spanish participants who are competing in the Olympic Games.

"It was a party with a few Australians and two of the Spanish king's nephews as well as Crown Prince Frederik, Prince Joachim, Prince Nikolaos of Greece and Princess Märtha Louise of Norway," she recalled. "I did not know who they were."

Over the next three years, the two were often seen together in Australia and Denmark. But it wasn't until 2003 when Queen Margrethe acknowledged their relationship. After six months, the palace announced their engagement. Donaldson and Crown Prince Frederik married on May 14, 2004 in Copenhagen, and she became an official member of the Danish royal family. The couple now has four kids.

Meanwhile, Prince William and Middleton met at the University of St. Andrews where they attended college together. According to the Duchess of Cambridge, she couldn't help but blush during their first encounter.

"I actually went bright red when I met you and scuttled off feeling very shy about meeting you," Middleton told Prince William about their first meeting. "William wasn't there for quite a bit of the time initially, he wasn't there from Fresher's Week, so it did take a bit of time for us to get to know each other. But we did become very close friends from quite early on."

It was later learned that Middleton did something that made her scuttled. She reportedly curtsied when she saw Prince William that accidentally caused the duke to spill a drink on himself.

Prince William and Middleton tied the knot on April 29, 2011. They now have three children, Prince George, Princess Charlotte and Prince Louis.