A rare photo showing the six children of King George V and Queen Mary shows a young Prince John, who was kept out of the public eye and later dubbed the 'Lost Prince'.
The photograph from 1909, which has been autographed by several of the royal children, is now being sold at auction and is expected to fetch around £3,000.
A four-year-old Prince John can be seen sitting on the knee of his oldest brother, Edward - who became King Edward VIII in 1936 and reigned for just 326 days after he abdicated the throne to marry American socialite and divorcee Wallis Simpson.
John, however, had been kept away from the public due to his epilepsy, and is now thought to have also been autistic.
Tragically, he ended up dying in 1919 at the age of 13 after suffering a seizure.
The photograph is being sold by a private collector with International Autograph Auction, of Malaga, Spain.
Set to fetch €2,500-€3,500 (£2,253-£3,153), the sale will take place on 22 July.
The description reads: "A fine and extremely rare vintage signed sepia 4.5 x 3.75 photograph by all six children of King George V and Queen Mary individually comprising Prince Edward of Wales (1894-1972, later King Edward VIII and afterwards Duke of Windsor), Prince Albert of Wales (1895-1952, later King George VI), Princess Mary of Wales (1897-1965, later Princess Royal and Countess of Harewood), Prince Henry of Wales (1900-1974, later Duke of Gloucester), Prince George of Wales (1902-1942, later Duke of Kent) and Prince John of Wales (1905-1919), the private family image dating from around 1909 and depicting the siblings standing and seated together in full length poses, most in formal attire and Princes Henry and George both wearing sailor's uniforms.
"Signed by each in bold, dark fountain pen inks with their names alone to clear areas of the image. Signed photographs by all six children of King George V and Queen Mary are extremely rare owing to Prince John's tragically early death from an epileptic seizure at the age of 13."
Auctioneer Francisco Pinero said: "This item is significant because it is extremely difficult to find a signed photo by all six children of King George V.
"Prince John was sent to Sandringham House and kept away from the public eye, therefore his autograph is very rare.
"The photo was probably given to a member of the Royal Family, someone close to it or perhaps a royal nanny."
In 2015, a letter written by Edward shortly after his brother's death was also uncovered.
In the cold-hearted message, Edward explained how he only considered John 'a brother in flesh' and 'more of an animal'.
He also said the family only ever visited his brother 'once or twice a year' and that his death had been the 'greatest relief imaginable' to them.
John spent his final two years of life separated from his siblings living in Wood Farm on the Sandringham Estate, and was looked after by his nanny Charlotte 'Lalla' Bill.
Queen Mary had overseen the decoration of John's bedroom, and after dropping him off in 1917 wrote: "It is very sad to see this great strong boy, with the mind of a child of six, and makes one quite unhappy."
John was also the subject of a 2003 BBC drama called The Lost Prince, which Daniel Williams playing the young royal and Gina McKee featuring as Lalla.
Directed by award-winning director Stephen Poliakoff, the drama won an Emmy Award in September 2005.
Featured Image Credit: International Autograph Auctions Europe SL
Topics: UK News, News, Royal Family