Princess Diana‘s children, Prince William and Prince Harry, and her grandchildren, whom she never met, visited her grave on Sunday. The Princess died nearly 20 years ago. Her family visited the grave in honor of her birthday. She would have turned 56-years-old on July 1.

Prince Charles, Diana’s ex-husband, was in Canada with his wife Duchess Camila of Cornwall and was absent from the event.

Prince William’s family, including Duchess Kate of Cambridge and their two children Prince George and Princess Charlotte took part in a private rededication service. Diana’s siblings and Prince Harry also took part in the service.

The service took place in the Althorp House in Northamptonshire and was overseen by the Justin Welby, Archbishop of Canterbury, the principal leader of the Church of England.

Diana’s children have discussed honoring their mother on several occasions earlier this year. William was 15-years-old at the time of his mother’s death and Harry was 12. The two have marked the anniversary – their mother died in a car accident in 1997 – by commissioning a statue of the late Princess in the public gardens at Kensington Place in London. The statue will be erected in August.

The Princess’ gravesite has been undergoing a multimillion-dollar revamp that began in 2015. It is the first major renovation undertaken by Althrop in nearly 350 years according to The Telegraph.

In honor of her birthday and her death, many members of the public have left balloons, flowers, photos, and cards on the gates of Buckingham Palace.

Others took to social media to wish Diana a happy birthday and to honor her memory.

“Happy Birthday to Princess Diana – she’d be 56 today (and the grandmother of 2),” Arianna Huffington simply wrote.

Motivational speaker John McGrath took to Twitter to share a quote of Diana’s. “Anywhere I see suffering, that is where I want to be doing what I can.”

Princess Diana died on August 31, 1997. She was buried seven days later.