The 96-year-old monarch will reportedly by joined by Prince Charles, Prince William and Prince George for the appearance after the Jubilee Pageant on June 5. Royal sources said the Queen “wants the world to see the heartbeat of her family and the future of the monarchy”.
Camilla and Kate are set to join their husbands for the balcony moment.
Princess Charlotte, seven, and Prince Louis, four, could also take part alongside eight-year-old George.
Other members of the Royal Family are expected to watch from the royal box in the grandstand at The Queen Victoria Memorial outside the palace.
A royal source told the Mirror: “Her Majesty believes it will send a strong message to the world, that despite the family’s trials and tribulations over the past few years, those at the very top are united in getting on with the job, sharing her sense of duty and dedication to serving the people of this country and the Commonwealth.”
Celebrations for the Queen’s Platinum Jubilee take place over a four-day weekend which kicks off next Thursday.
The festivities will begin with the military spectacle of Trooping the Colour on June 2.
More than 1,500 officers and soldiers and 250 horses from the Household Division will stage the display on Horse Guards Parade in central London, with the colour trooped by the 1st Battalion, Irish Guards.
Some 400 musicians from 10 military bands and corps of drums will march amid pomp and pageantry.
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A traditional service of thanksgiving will be held at St Paul’s Cathedral in central London on Friday June 3.
Epsom Derby Day on Saturday June 4 could see the Queen head to the races where there will be a special tribute from the world of racing.
In the evening, Queen + Adam Lambert will open the BBC’s Party at the Palace entertaining a live audience of 22,000 people.
On Sunday June 5, more than 70,000 Big Jubilee Lunches are being held across the UK, with an expected 10 million people set to sit down with their neighbours at street parties, picnics and barbecues.
The Jubilee Pageant will also take place through the streets of London.
Set to be watched by up to a billion people across the globe, more than 10,000 people will be involved in the £15 million procession.
The Queen, who has recently suffered from mobility issues, is said to be looking forward to the commemorations.
Buckingham Palace has said her presence at the Jubilee events may not be confirmed until the day.