Charles Spencer's wife Karen moved her followers at the weekend, when she shared a beautiful shot of Princess Diana's final resting place to Instagram.
On Wednesday, the Earl himself took to the social media site to share an incredible and never-before-seen family throwback.
Posting a black-and-white shot of two children – an older girl and her younger brother, it was taken close to the family's Northamptonshire estate and the resemblance to Charles and his sister was clear.
The father-of-seven penned: "Just discovered – this photograph, taken by my great-grandmother Margaret Spencer in c.1900, of my grandfather Jack, and his eldest sister Delia.
"A lovely family moment, in late Victorian England. They are photographed at a spot I know well, near Althorp. I wonder what Aunt Delia has on her lap…?"
His followers were quick to note the family similarity, with one writing: "That could be you and Diana. The resemblance is striking," and another agreeing: I thought the same – you could have recreated it at the same age had you seen the picture earlier."
Another eagle-eyed fan, meanwhile, noticed that Delia appeared to have a hat on her lap and to be holding a pair of binoculars. The Earl moved to Althorp with his family when he was 11 and Diana was 14, while their older sisters Sarah and Jane were already adults.
Now 59, Charles has no doubt been spending a lot of time thinking back to his childhood, as he prepares for next month's release of his memoir about his time at boarding school.
Earlier this year, he shared an image of himself behind a microphone, reading the audiobook, which he paired with a caption about what he described as "an uncompromising book".
In an emotional caption, the father-of-seven wrote: "In the studio today, narrating the audiobook of A Very Private School, for publication day - 12 March, by @gallerybooks, in the USA, and 14 March, by @wmcollinsbooks, in the UK. A relief to hear my words. And know that every sentence rang true, about the school I attended when aged 8 to 13."
He went on: "It's an uncompromising book - the saddest parts come not from me (I'm just the way in to the tale), but from my contemporaries, who've suffered in silence for 50 years.
"Last week one of my friends there told me that my writing this book had prompted him to tell his wife of 38 years, for the very first time, what he went through as a boy. They cried together, for an hour…"
Charles' followers were full of compassion and shared their encouragement about the book, both on that post and when the memoir was first announced.
When he first publicly shared the cover image, which shows himself as a young boy, Karen re-posted it to her Instagram account, commenting: "My husband Charles has written a book about his experience at the boarding school he was sent to at age 8. It's titled 'A Very Private School' it's being released in March, but you can preorder now.
As a mother, this photo of him, aged 8, about to leave his home just breaks my heart."