The Duke and Duchess of York, with their daughters the Princesses Elizabeth and Margaret, along with their dogs, in June 1936, on the grounds of Windsor Castle.
In the same month, the future King George VI’s brother ascended the throne, only to abdicate in December.
Original B&W photo
George VI, shortly before he died, with his family. Queen Elizabeth, his wife and later Queen Mother is on the left in this photo with Prince Charles. Next to her is Princess Margaret, with Prince Philip at the back. Princess Elizabeth, the present Queen, is standing by the pram in which sits Princess Anne.
The flowers in the background and the clothing, together with Anne being in a pram (she was born in August 1950), suggests to me that this photo was taken in the spring of 1951.