Queen Elizabeth II turns 96 on Thursday, and her son Prince Charles and grandson Prince William, along with their spouses, are leading the royal tributes for the reigning monarch.

"Wishing Her Majesty The Queen a very happy 96th birthday today! An inspiration to so many across the UK, the Commonwealth and the world, it’s particularly special to be celebrating in this #PlatinumJubilee year," Prince William and Kate Middleton wrote on Twitter.

Prince Charles and his wife Camilla, the Duchess of Cornwall, also marked the queen's special day with a series of photographs of the queen over the years.

QUEEN ELIZABETH II PRIVATELY MARKS HER 96TH BIRTHDAY, GETS OWN BARBIE DOLL FOR PLATINUM JUBILEE

"Wishing Her Majesty The Queen a particularly special 96th birthday today, as we celebrate her Platinum Jubilee year," the Prince of Wales and duchess' tweet reads.

The official Twitter account for the royal family also shared a photograph of the queen at the age of 2.

"Then, in 1928, it was never expected she would be Queen, and this year Her Majesty is celebrating her #PlatinumJubilee - a first in British history," the tweet reads.

The queen is said to be marking her 96th year in private on Thursday at the Sandringham estate in eastern England, which Elizabeth often retreated to with her late husband Prince Philip, who died in April 2021.

QUEEN ELIZABETH POSES WITH HER PONIES AHEAD OF 96TH BIRTHDAY

Elizabeth is expected to spend the day at the estate’s Wood Farm cottage, a personal sanctuary where she also spent her first Christmas since Philip’s death. Philip loved the cottage, in part because it is close to the sea, she said in February when hosting a rare public event at Sandringham.

This birthday comes during the queen’s platinum jubilee year, marking her 70 years on the throne. While Thursday will be low-key, public celebrations will take place June 2-5, when four days of jubilee festivities have been scheduled to coincide with the monarch’s official birthday.

In a televised interview that aired this week, Prince Harry opened up about his grandmother and her significant milestone.

Harry touched on reports that he wants to return to his homeland in June for his grandmother's platinum jubilee celebrations, but briefly cited ongoing security concerns that could come in the way of that.

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Britain's Queen Elizabeth II is marking her 96th birthday privately on Thursday, April 21, 2022 retreating to the Sandringham estate in eastern England that has offered the monarch and her late husband, Prince Philip, a refuge from the affairs of state.  (AP)

"I don't know. There's lots of things right now, security issues, and everything else, so this is what I'm trying to do. I'm trying to make it possible so I can get my kids to meet her," Harry shared.

While Harry joked that his grandmother may be getting "bored of her birthdays," he shared what he feels is the best thing about the reigning monarch.

"Her sense of humor and her ability to see the humor in so many different things. We have a really special relationship. We talk about things that she can't talk about with anybody else," the 37-year-old said.

Prince Harry and Meghan Markle met with Queen Elizabeth II last week. (Pool/Max Mumby)

Harry's comments come on the heels of a special visit he and his wife, Meghan Markle, paid to Queen Elizabeth ahead of the Invictus Games in the Netherlands. It was the first time the duke and duchess of Sussex saw the queen in the United Kingdom since they stepped away from royal duties and moved to California in 2020.

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Harry, in an interview with NBC, said his grandmother was "on great form," though he added that he wanted to make sure she was "protected" and had "the right people around her."

Queen Elizabeth Kate Middleton Prince William

Catherine, Duchess of Cambridge, Queen Elizabeth II and Prince William. (Samir Hussein/WireImage)

Britain’s longest-serving monarch, Elizabeth has spent much of the past two years at Windsor Castle, west of London, where she took refuge during the pandemic.

The Associated Press contributed to this report.