Princess Diana's brother Charles Spencer shares rare childhood photo with his sister and mum

Much to the delight of royal fans, Princess Diana's brother Earl Charles Spencer has shared a rare childhood photo of the mother of two.

Taking to social media, the 59-year-old posted a sweet throwback picture of himself, the 'People's Princess' and their mother.

In the adorable snap, Princess Diana can be seen in shorts and a t-shirt, while standing next to Earl Spencer who is all smiles sitting on a swing.

"My mother, Diana and I, in c. 1967." Charles captioned the sentimental post, "I would have been 3, and Diana 5 or 6. I love how happy each of us looks."

Charles also shared about how he got his childhood nickname, "At this stage of my life, my mother nicknamed me “Buzz” - because she saw me as having the endless energy of a rather happy - and busy - bee."

It has been 27 years since Princess Diana died at the age of 36, when the car she was travelling in crashed in a Paris tunnel on August 31, 1997.

Born on July 1, 1961, Diana also grew up with her two sisters, Sarah and Jane. She also had an older brother, John Spencer, who died shortly after his birth.