Charles Spencer/Instagram; Georges De Keerle/Getty Princess Diana's younger brother, Charles Spencer, honored her on what would have been her 64th birthday The late Princess of Wales died at age 36 in 1997 and would have turned 64 on July 1 The 9th Earl Spencer shared a new photo captioned, "Another July 1st, from long ago" showing them together at her 6th birthday party Princess Diana's brother,Charles Spencer, is remembering her on what would have been her 64th birthday. On July 1, the 9th Earl Spencer posted a previously unseen photo of himself with his elder sister. The black-and-white childhood throwback showed Charles and Diana riding a camel at a celebration identified as her 6th birthday party. "Another July 1st, from long ago - 1967, in fact: for Diana's 6th birthday party, my father (standing, left) - to huge excitement - secured the services of Bert the Camel, from Peterborough Zoo," Charles, 61, wrote below the photo onInstagram. Princess Diana was the third daughter born toJohn SpencerandFrances Shand Kydd, and she grew up with elder sisters,Lady Sarah McCorquodale and Lady Jane Fellowes, and younger brother, Charles. She became a princess when she married the futureKing Charlesin 1981, and they went on to welcome two sons,Prince WilliamandPrince Harry. Charles and Diana separated in 1992 and divorced in 1996, amid speculation of marriage trouble and infidelity by both parties. Princess Diana died on Aug. 31, 1997 at age 36 following a car accident in Paris, while the vehicle she was traveling in was pursued by paparazzi. The 9th Earl Spencer famously delivered apassionate eulogyat his sister's royal ceremonial funeral in 1997 and continues to honor her memory today. In May, Charles appeared onLoose Men, a special edition of the ITV talk showLoose Womenfor Mental Health Awareness Week,where he spoke about the enduring pain of sibling grief. David M. Benett/Dave Benett/Getty; Tim Graham Photo Library via Getty "It's such an amputation. It's like the other guys were saying, you grow up with these people, they are your flesh and blood, they're with you forever, and then they're gone," said Charles, an author and historian. "For years after Diana died, I would think, 'I must ring her and tell her something,' because we shared the same sense of humor and you just realize, of course, that's not going to happen," he added about the deep bond they shared. Over the weekend, the author ofA Very Private School: A Memoirposted a photoof the gallery wall including a portrait of Diana atAlthorp House, the Spencer family's ancestral home in Northamptonshire, England, and last week, he shared another previously unseen picture with his sister. 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! "Trying to remember what this rather formal family photograph was for — it shows my sisters and brothers-in-law, flanking my father and stepmother, at the base of the main staircase (in the central hallway, known as the Saloon) at@althorphousein the late '80s. Perhaps it was something to do with my father's 65th birthday, in January 1989?" Earl Spencer wrote below theInstagramphoto. "Definitely an '80s air to it all," he added in part. Read the original article onPeople