Archie and Lilibet Mountbatten-Windsor's titles are yet to officially change.
The children of Prince Harry and his wife Meghan, the duchess of Sussex, are able to use HRH titles if they wish now their grandfather, King Charles, is monarch following the death of Queen Elizabeth.
But a royal spokesperson said they were awaiting confirmation about how the children would be known.
Since the queen passed away last Thursday, the royal family's website has updated the line of succession, complete with Harry's brother Prince William's change in title to the Prince of Wales, while his and wife Catherine, Princess of Wales' children have had their names amended too, with the order listing them as Prince George, Princess Charlotte and Prince Louis "of Wales", updated from "of Cambridge".
However, Archie, three, and 15-month-old Lilibet, who are sixth and seventh in line to the throne respectively, are noted as "Master" and Miss".
Asked why that was, a spokesperson for the king said it was because Charles had announced William and Catherine's titles as Prince and Princess of Wales during his address to the nation on Friday but had simply expressed his love for Harry and Meghan, who stepped away from royal duties and moved to the US two years ago.
The spokesperson added: "While the website was updated for the Waleses, clearly updating love on a website doesn't quite work so we've not quite done that but clearly he does love them.
“We will be working through updating the website as and when we get information."
Asked if Archie and Lili would take on the titles of prince and princess, he added: "At the moment, we're focused on the next 10 days and as and when we get information, we will update that website."
In his speech, Charles confirmed his eldest son would take on his former role of Prince of Wales, one of the only titles which wasn't automatically passed down.
The king said: “As my heir, William now assumes the Scottish titles which have meant so much to me.
“He succeeds me as Duke of Cornwall and takes on the responsibilities for the Duchy of Cornwall, which I have undertaken for more than five decades.
“Today, I am proud to create him ‘Prince of Wales’ – ‘Tywysog Cymru’ – the country whose title I have been so greatly privileged to bear during so much of my life and duty.
“With Catherine beside him, our new prince and princess of Wales will, I know, continue to inspire and lead our national conversations, helping to bring the marginal to the centre ground, where vital help can be given.
“I want also to express my love for Harry and Meghan, as they continue to build their lives overseas."