The six will attend Prince Louis' christening on Monday, taking part in what is expected to be a traditional ceremony at the Chapel Royal in St James's Palace.
The monarch was due to return to London on Monday before a busy schedule of events including a meeting with U.S. President Donald Trump on Friday at her Windsor Castle home.
The young prince was baptised using water from the River Jordan.
Another, taken just 22 years later, captures the proud Princess holding her eldest son, Prince Charles, on his own big day in December 1948. As after George and Charlotte's baptisms, guests will be served slices of the duke and duchess's wedding cake.
Princess Charlotte is proving, yet again, that she's nailed the royal wave technique.
Prince Louis Arthur Charles of Cambridge, fifth in line to the throne, was born on St George's Day, April 23, at the private Lindo Wing of St Mary's Hospital in Paddington, London, weighing 8lb 7oz.
It's days like today that make being a mom so special for Kate Middleton.
In addition to the cake, Prince Louis's christening gown was also recycled. He is a close friend of both Prince William and Prince Harry - helping to organise the former's stag do - and was dubbed the pair's "court jester".