The Duke and Duchess of Cambridge and Prince Harry are to attend a private service to re-dedicate the grave of Diana, Princess of Wales at her family home Althorp House.
Diana is buried in the grounds of Althorp House in Northamptonshire and the service will be held on the day of her birth - July 1.
Kensington Palace said in a brief statement: "The service, which will fall on what would have been the Princess's birthday, will be conducted by The Archbishop of Canterbury and attended by her family."
The re-dedication of Diana's grave comes a few months before the 20th anniversary of her death.
William was 15 and his brother Harry just 12 when their mother was killed in a car crash in Paris on August 31 1997, a death that shocked the world.
The royal brothers are commemorating the anniversary by commissioning a statue of their mother which will stand in the public gardens of her former home Kensington Palace in London.
And the Diana Award - a charity established to promote the Princess's belief in the positive power of young people - is staging a year-long celebration of her qualities of kindness, compassion and service.
It is understood that William and Kate will be joined by their children Prince George and Princess Charlotte at the service and it is likely Diana's brother Earl Spencer will lead his family.
Diana is buried on an island in an ornamental lake known as The Oval within Althorp Park's Pleasure Garden.
Countess Spencer, the Earl Spencer's wife, has been overseeing an extensive redesign of the Oval Lake to honour Diana's memory.