Kate Middleton is 43!

The Princess of Wales is celebrating her birthday surrounded by those nearest and dearest to her on Thursday, The Post can reveal.

Princess Catherine has been enjoying her time at Sandringham Estate in Norfolk, England during the festive break. However, she is expected to spend the special day at Adelaide Cottage, the Wales’ family home.

As for the celebration itself, King Charles’ former personal butler Grant Harrold says it will be an intimate, family-filled affair.

According to royal expert Harrold, it is anticipated that the King and Queen will host a dinner for her at either Clarence House or Highgrove. Harrold, who worked for the king for seven years, expressed confidence in the King’s ability to organize such events.

Additionally, Harrold mentioned that William will ensure there is a lovely meal and some gifts for the celebration. The festivities will also involve the children, who are eager to join in the celebrations with Princess Catherine.

While the mom of three’s birthday is often a low-key event, given its proximity to Christmas, this year’s celebrations may look slightly different given the difficult year Middleton has had health-wise.

As Princess Catherine is “returning back to royal duties and obviously is doing well with her treatment,” Harrold suspects that the princess’ parents, Carole and Michael Middleton, will join in on the celebration.

The former royal staffer believes Middleton may hear well-wishes from two estranged members of the royal family: Prince Harry and Meghan Markle.

“I think Harry and Meghan will reach out to wish her happy birthday,” Harrold told The Post on behalf of Slingo. “I always get the impression that despite the damage within the family, I still think they would reach out to each other.”

“So whether that be a phone call, text message or WhatsApp an e-mail or a traditional card,” Harrold says, “It depends on the relationship. If it is improving, which is what I still think is happening, it’s possible that it will be a phone call.”

The same day Middleton rings in her 43rd birthday, Prince Edward will be jetting off to the US to represent the king and the rest of the royal family at former President Jimmy Carter’s funeral in Washington, D.C.