Royals Future Queens! Kate Middleton Reunites with Princess Mary of Denmark: Inside Their Royal Friendship The commoners-turned-royals have supported each other since first meeting in 2011 By Erin Hill Erin Hill Twitter Senior News Editor, PEOPLE People Editorial Guidelines Published on February 23, 2022 08:00 AM Share Tweet Pin Email The Duchess of Cambridge and Crown Princess Mary of Denmark. Photo: Samir Hussein/WireImage On the final day of her royal tour in Denmark, Kate Middleton had a special private lunch with Crown Princess Mary. The two royals, who will one day be Queens of their countries, have become friends over the years. They first met during Prince William and Kate's official visit to Denmark in 2011 after their royal wedding. Mary and her husband Prince Frederik, who is heir to the throne in Denmark, also visited William and Kate in 2016. The couples attended Royal Ascot together. In addition to being each other's royal doppelgänger and sharing a similar style (chic coat dresses and long brunette locks!), Kate and Mary share a similar background. They are both commoners-turned-royals. Kate married Prince William in 2011 after meeting at St. Andrews University in 2001, and Mary, a native of Australia, wed Prince Frederik in 2004 after they met at a pub in Sydney during the 2000 Olympics. Kate Middleton Confesses She's 'Very Broody': 'I Come Home Saying Let's Have Another One' Kate Middleton and Princess Mary. CLAUS BECH/Ritzau Scanpix/AFP via Getty Images They also both have a passion for championing women's and children's issues in their royal work. Last year, Kate founded launched The Royal Foundation Centre for Early Childhood—a hub within the Cambridges' charitable vehicle that will help push for increased awareness of and new research into the impact of the early years. The Danish royal founded the Mary Foundation in 2007 to protect vulnerable women and children from domestic violence. Kate Middleton and Princess Mary in 2011. Indigo - Pool/Getty Images Kate and Mary will also likely chat about each other's children over their lunch at Frederik VIII's Palace, where Mary lives with her family. Kate is mom to Prince George, 8, Princess Charlotte, 6, and Prince Louis, 3. And Mary is a mother of four. She and Frederik are parents to Prince Christian, 16, Princess Isabella, 14, and 11-year-old twins Prince Vincent and Princess Josephine. Kate Middleton and Princess Mary at Royal Ascot in 2016. Max Mumby/Indigo/Getty Images Can't get enough of PEOPLE's Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more! And they both have milestone birthdays to toast to! Kate celebrated her 40th birthday on January 9 and Mary turned 50 on Feb. 5. After lunch, Kate will accompany Mary to see first-hand the work of the Mary Foundation before she heads home to the U.K.