Earl Spencer shared a touching photograph as he marked a poignant day on Tuesday.
Diana, Princess of Wales, who tragically died in a car crash, aged 36, in 1997, would have marked her 64th birthday on 1 July.
Her younger brother, Charles, 61, recalled a fun memory from their childhood as he marked the day in an Instagram post.
The black and white shot showed Diana and Charles smiling while sitting on a camel, as their father, John Spencer, looked on.
"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," the Earl wrote in the caption.
Many fans commented with well-wishes for the late princess, with others commenting, "beautiful photo," "lovely photo" and "fantastic picture".
© GettyDiana was the third child born to John Spencer and Frances Shand Kydd, and she grew up with her siblings, Lady Sarah McCorquodale, Lady Jane Fellows, and Charles, firstly at Park House in Norfolk, before the Spencers moved to the family seat at Althorp House in Northamptonshire.
Charles has been custodian of Althorp since his father's death in 1992, helping to restore the Grade I stately home and regularly sharing updates about the vast estate on social media.
Symbol of selfless humanity
The Earl is close to his nephews, Princes William and Harry, and walked besides them during Diana's funeral procession. He also delivered a powerful eulogy at the service at Westminster Abbey.
© GettyPaying tribute to his sister, Charles said in his speech: "Diana was the very essence of compassion, of duty, of style, of beauty. All over the world she was a symbol of selfless humanity.
"All over the world, a standard bearer for the rights of the truly downtrodden, a very British girl who transcended nationality.
© Getty"Someone with a natural nobility who was classless and who proved in the last year that she needed no royal title to continue to generate her particular brand of magic."
Following her death, Diana was laid to rest on a small island in the middle of the Round Oval lake at Althorp.
