Kate Middleton reportedly received a special surprise from Meghan Markle and Prince Harry for her 39th birthday.

The Duchess of Cambridge, whose birthday was on Jan. 9, was "taken aback" when she saw the unexpected gifts and card from her brother-in-law, 36, and his wife, 39.

"It was a nice surprise," a source told Us Weekly on Wednesday. "Kate wasn’t expecting anything from the couple."

According to the royal insider, Middleton had a "low-key" celebration with her husband Prince William, 38, as well as their three children: Prince George, 7, Princess Charlotte, 5, and Prince Louis, 2.

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Kate Middleton and Prince William pose for a photo with their three children, George (right), Charlotte (middle) and Louis.

Kate Middleton and Prince William pose for a photo with their three children, George (right), Charlotte (middle) and Louis. (AP)

According to the outlet, the surprise from the Duke and Duchess of Sussex came shortly after news broke that the couple, who are currently residing in California, is slated to travel back to the U.K. later this year to participate in several royal events. Queen Elizabeth II, William and Harry’s grandmother, turns 95 in April. Her husband Prince Philip turns 100 in June.

In addition, William and Harry are expected to appear for the statue unveiling of their late mother Princess Diana in Kensington Palace. The Princess of Wales would have turned 60 in July. 

Last summer, royal reporters Carolyn Durand and Omid Scobie released their bombshell book "Finding Freedom," where numerous palace insiders came forward and detailed what led to the Duke and Duchess of Sussex’s departure as senior members of the British royal family.

The Sunday Times reported that Middleton allegedly didn’t instantly roll out the red carpet for the former American actress when she began dating Harry.

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The Duke and Duchess of Sussex (right) reportedly gave a sweet birthday surprise to the Duchess of Cambridge (left).

The Duke and Duchess of Sussex (right) reportedly gave a sweet birthday surprise to the Duchess of Cambridge (left). (Getty)

"Though it was not necessarily her responsibility, Kate did little to bridge the divide," wrote Scobie and Durand.

The authors insisted that while the duchesses "were not at war with each other," there were some "awkward moments."

According to the book, Middleton felt she and the "Suits" star didn’t have much in common "other than the fact that they lived at Kensington Palace."

Katie Nicholl, a royal correspondent for Vanity Fair, pointed out that friends of the Duke and Duchess of Cambridge spoke to the Mail on Sunday, insisting the couple had "done all they possibly could" to welcome Markle into the royal family. They claimed Middleton personally cooked vegan meals for Markle during a visit to their home at Anmer Hall.

ROYAL KIDS GEORGE, CHARLOTTE, LOUIS MAKE RED CARPET DEBUT WITH PRINCE WILLIAM, KATE MIDDLETON AT SHOW

According to 'Finding Freedom,' Kate Middleton (right) allegedly felt she and Meghan Markle (left) didn't have much in common 'other than the fact that they lived at Kensington Palace.'

According to 'Finding Freedom,' Kate Middleton (right) allegedly felt she and Meghan Markle (left) didn't have much in common 'other than the fact that they lived at Kensington Palace.' (Getty)

Still, Scobie and Durand wrote, the women "struggled to move past distant politeness."

Markle initially hoped Middleton would "show her the ropes" in being a member of "The Firm." But the book claimed that Middleton, who was pregnant at the time with Prince Louis, was distant toward her.

"[Kate] was fiercely loyal to her husband and family," they pointed out.

Vanity Fair reported on Monday that at one point, Middleton brought flowers to Markle as a peace offering. However, Meghan "told Kate in no uncertain terms that flowers were not enough."

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Meghan Markle and Prince Harry currently reside in California with their son Archie.

Meghan Markle and Prince Harry currently reside in California with their son Archie. (Photo by Steve Parsons - WPA Pool/Getty Images)

Scobie and Durand shared that Harry, in particular, was "deeply saddened" by the growing distance between him and his older brother William and Middleton. He had hoped their children would grow up together.

While it was initially reported that Harry and Markle cooperated with the authors, reps for the couple confirmed to Fox News that they played no part in the book.

"The Duke and Duchess of Sussex were not interviewed and did not contribute to ‘Finding Freedom,’" said the statement. "This book is based on the authors’ own experiences as members of the royal press corps and their own independent reporting."