▲The Duke and Duchess of York hold their first daughter, the Royal Highness the Princess Beatrice Elizabeth Mary of York. She was born on August 8, 1988.

▲Princess Eugenie Victoria Helena arrived less than two years later, on March 23, 1990.

▲The young family at the christening of Princess Eugenie with two of her cousins, Zara Phillips and Prince Harry.

▲The Duchess of York arrives at London's Heathrow airport from Argentina with her daughters.

▲The Duke and Duchess of York at Wentworth Golf Club, Surrey, with their daughters for the Duchess of York's fifth Celeb-Am Golf tournament in aid of the Motor Neurone Disease Association.

▲The girls try their hands at golfing.

▲Dressed alike at the golf tournament.

▲Princess Beatrice poses with her mother on her first day of school at St. George's in 2000.

▲Sarah Ferguson arrives with her daughters for the world premiere of 'Harry Potter and the Philosopher's Stone' on November 4, 2001 in London.

▲The Duchess of York shows off her bag featuring a picture of her daughters in 2003.

▲Mother and daughters pose for photographers while on vacation in Switzerland in 2004.

▲At the UK premiere of 'The Aviator' in 2004.

▲At the final of the Veuve Clicquot Gold Cup in 2005.

▲On the way to the ceremony in 2006. The annual event has been a part of the princesses' lives since birth.

▲A moody looking Eugenie with her mother at the launch party for British couture label Marchesa's Spring/Summer 2006 collection.

▲Accepting flowers from children as they leave the Christmas Day service at Sandringham with their grandmother, the queen, in 2006.

▲Sarah Ferguson and Princess Beatrice walk the catwalk as part of the Fashion Relief Show during London Fashion Week 2007.

▲Leaving Westminster Abbey after a service celebrating the 60th wedding anniversary of the Queen and Prince Philip in 2007.

▲Sharing a laugh with Autumn Phillips during Ladies' Day at Royal Ascot in 2008.

▲Prince Andrew and Princess Eugenie visit the debris of the Sichuan earthquake in 2008.

▲Arriving at the Form Menswear launch at Harrods in 2008.

▲Princess Beatrice arrives at Goldsmiths, University of London to begin a degree in the History of Ideas in 2008.

▲At the World Premiere of 'The Young Victoria' in 2009.

▲At the Toronto International Film Festival in 2009.

▲Here they are glittering in LA in 2009.

▲Members of the royal family disembark the Hebridean Princess in 2010. The princesses carry their own bags.

▲On the same trip, the family enjoyes a private tour around the Western Isles of Scotland.

▲Watching the troops fly from the balcony of Buckingham Palace with their cousin Prince William in 2010.

▲At the wedding of Prince William and Kate Middleton in 2011.

▲The princesses recently told Vogue that they cried after reading the public mockery of the bold hats they wore to this event.

▲Arriving at the opening day of Royal Ascot in 2011.

▲At a fundraising day on behalf of Prince Harry's charity Sentebale in 2011.

▲The princesses watch the action with their grandfather, Prince Philip, at the start of the weekend marking the Queen's Diamond Jubilee celebrations, at Epsom Racecourse in 2012.

▲Sharing a joke with their cousin, Prince Harry, on the balcony of Buckingham Palace after the Trooping the Colour ceremony in 2012.

▲Princess Eugenie attends her graduation ceremony at Newcastle University in 2012.

▲Watching the track cycling on Day 6 of the London 2012 Olympic Games.

▲Prince Harry, Princess Eugenie, and Princess Beatrice watch the Eventing Cross Country Equestrian event on Day 3 of the London 2012 Olympic Games.

▲At the Big Jubilee Lunch in celebration of the Diamond Jubilee of Queen Elizabeth II in 2012.

▲Waving from a barge in a flotilla of 1,000 vessels during the Diamond Jubilee Thames River Pageant in 2012.

▲Leaving a Service Of Thanksgiving at St Paul's Cathedral in 2012.

▲In Germany in 2013, supporting the government's GREAT initiative promoting the UK abroad.

▲Posing next to a Mini in front of Brandenburg Gate as part of their German trip.

▲At Hanover City Hall on the second day of the visit to Germany in support of GREAT.

▲Arriving at the 2013 event with their father.

▲At the Derby Festival in Epsom in 2013.

▲Arriving at Day 1 of Royal Ascot in 2013.

▲At Ladies' Day on Day 3 of Royal Ascot in 2013.

▲And back at the event in 2014.

▲Beatrice wears burnt orange to Day 3 of Ascot in 2014.

▲At the Annual Charity Day hosted by Cantor Fitzgerald and BGC in 2015.

▲During Day 4 of Royal Ascot in 2015.

▲Ladies' Day at Ascot in 2015.

▲Arriving at the ceremony in 2015.

▲Press day at the Chelsea Flower Show in 2016.

▲Princess Beatrice recycles a hat from 2014 for the annual event.

▲With their father during The Patron's Lunch celebrations for the Queen's 90th birthday in 2016.

▲Princess Eugenie and Princess Beatrice arrive for a service of thanksgiving for Queen Elizabeth II's 90th birthday at St Paul's cathedral.

▲Day 3 of Royal Ascot in June 2016.

▲Attending a Buckingham Palace garden party for The Not Forgotten Association in May 2016.

▲In pretty florals for the 2017 event.

▲Princess Beatrice and Princess Eugenie attend the V&A summer party in June 2017.

▲In the Parade Ring at Royal Ascot 2017 on Ladies' Day.

▲The princesses take part in the Royal Parade during Royal Ascot Day 3 in 2018.

▲Prince Charles, Prince of Wales, Camilla, Duchess of Cornwall, and the sisters on Day 1 of Royal Ascot in 2018.

▲At We Day UK at Wembley Arena in March 2018.

▲In St George's Chapel ahead of the wedding of Prince Harry and Meghan Markle on May 19, 2018.

▲With the next generation of royals, including the newly married Duke and Duchess of Sussex, at Trooping the Colour 2018.

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Princess Beatrice helps sister Eugenie with her train after her wedding to Jack Brooksbank in October 2018.

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Princess Beatrice of York has been in the news as of late due to speculation that she may be announcing her own royal wedding very soon, this with boyfriend Edoardo Mapelli Mozzi. However, while they seem to have an increasingly close relationship, there is another partnership in her life that has lasted even longer: that of her sister, Princess Eugenie. The sisters are less than two years apart in age, and have always seemed to have a special bond.

In honor of Princess Beatrice's 31st birthday, check out this gallery highlighting the sisters' relationship over the years.