The Duke and Duchess of Cambridge shared a photo of the royal family on the balcony of Buckingham Palace watching the annual Trooping the Colour parade in 2016, alongside the words: "Wishing a very happy 93rd birthday to Her Majesty The Queen!"
WATCH this adorable video to see royal fans sing happy birthday to Queen Elizabeth on Sunday!
Prince William and the Duke of Edinburgh were dressed in their military finery, while Her Majesty was a vision in striking green.
Prince Harry was just visible behind the head of his older brother.
The photo was taken three years ago before the Duchess of Sussex joined the Windsor family.
Royal enthusiasts were quick to speculate that Kate and William could easily have chosen a photo from Trooping the Colour in 2018 when Meghan was present.
The telling move adds fuel to the fire of royal rift rumours which have plagued both Kate and Meghan and William and Harry for months.
William, 36, and Harry, 34, did not engage with each other on the way in or out of St George's Chapel, People Magazine reports.
The brothers appeared rigid as they were separated by their cousin Zara Tindall and her husband Mike.
Soon-to-be dad Harry exchanged brief pleasantries with William's wife Kate Middleton, but never engaged with the future King himself.