The Cambridge children have made numerous appearances at celebrations for the Queen's Platinum Jubilee this weekend.
This included at Saturday night's star-studded concert, with the Duke and Duchess of Cambridge bringing Prince George, eight, and Princess Charlotte, seven, along to watch the show held in their great-grandmother's honour.
From front-row seats between their parents, the royal youngsters frequently beamed as they saw the likes of Diana Ross, Queen and Mabel perform onstage outside Buckingham Palace.
However, their appearance caused debate among viewers about whether it was correct they had come along for the evening event, which began at 7.30pm.
Posting on Twitter, one viewer at home wrote: "Am I the only one who thinks it's too late for George and Charlotte to be up?"
Another suggested that the performances might not be that interesting to the youngsters, commenting: "Princess Charlotte and Prince George look so bored in this concert at the palace."
Meanwhile, a third shared: "All the mums and grandmas now worried George and Charlotte will be getting a bit cold and tired now."
However, a fourth who was pleased by their presence noted: "Aww Prince George and Princess Charlotte at the concert tonight!"
And another added: "Great to see Prince George and Princess Charlotte enjoying themselves so much at the sing-song."
While the young prince and princess have accompanied the duke and duchess to royal engagements in the past, the frequency has increased this Jubilee weekend.
Earlier yesterday, they were seen with their parents greeting crowds at Cardiff Castle in Wales.
They were also present alongside the Queen on the Buckingham Palace balcony on Thursday with their younger brother Prince Louis, four, after having made their debut as a trio at Trooping the Colour.
This morning, a series of sweet images were released of them baking cupcakes for a street party with their mother.