Queen Elizabeth II is expected to meet Lilibet, Prince Harry’s daughter and her namesake, for the first time this weekend.
It will be Lilibet’s first visit to the UK after Prince Harry and his wife Meghan Markle retired from royal life and moved to California.
Lilbet takes her name from the queen's childhood nickname.
Details of the get-together have not been made public, but were reported by the British newspaper The Sun. However, the queen is no longer planning to attend the Epsom Derby on Saturday. That means there is a full day without her making a public appearance during her platinum jubilee celebrations.
The monarch, who has mobility issues that have prevented her from carrying out royal duties, wants to pace herself during the four-day national holiday that starts on Thursday.
The quiet day on Saturday is now seen as the ideal time for the monarch, 96, to meet Lilibet, Prince Harry and Meghan.
The queen is, however, still expected to delight crowds with two appearances on the Buckingham Palace balcony. The first will come after Trooping the Colour on Thursday, and the second will follow the Pageant parade finale on Sunday.
For the balcony appearances, the queen has limited the numbers to working royals, meaning the Duke and Duchess of Sussex will not be there.
Her great-grandchildren from the Duke and Duchess of Cambridge, William and Kate — Prince George, Princess Charlotte and Prince Louis — will be on the balcony.
A six-minute display by more than 70 aircraft will include the Red Arrows and the Royal Air Force Battle of Britain Memorial Flight.
The monarch is also hoping to be able to attend the Service of Thanksgiving at St Paul's Cathedral on Friday with her wider family. The Duke and Duchess of Sussex and the Duke of York are also expected to attend the service.
At the BBC's Party At The Palace concert in front of Buckingham Palace on Saturday night, both the Prince of Wales and the Duke of Cambridge are said to be set to pay public tributes to the queen. The star-studded event will feature acts such as Diana Ross and Queen.
The queen is not expected to be there and will watch on television instead from Windsor Castle.
On Sunday, more than 85,000 Big Jubilee Lunches and street parties are set to be staged in celebration of the queen's record-breaking 70-year reign.
Queen Elizabeth is not just the longest-reigning living queen, but also the longest-reigning living monarch.
The longest-reigning monarch ever was King Louis XIV, who presided over France for 72 years and 110 days from May 14, 1643 until September 1, 1715.