Kate Middleton had 'private' moment with Prince Harry, Meghan Markle on her birthday

Prince Harry and Meghan Markle got to greet Kate Middleton on her 40th birthday on Jan. 9 albeit they did it privately.

Members of the British royal family customarily send their birthday greetings online through their respective social media pages. Queen Elizabeth II, Prince Charles, and Camilla, the Duchess of Cornwall were among those who shared their well-wishes to the Duchess of Cambridge on her special day.

However, royal fans were more curious to know if the Duke and Duchess of Sussex were able to greet Kate Middleton on her birthday. According to American author Christopher Andersen, the couple got to spend time with the celebrant via video call because they no longer have an active Instagram and Twitter page.

"They did a video call. They wished her a happy birthday," the author of "Brothers and Wives: Inside the Private Lives of William, Kate, Harry, and Meghan" told US Weekly.

He said it was "very private" and that Prince Harry and Meghan Markle "were not about to post anything the way they did two years ago." Andersen noted that it was different from how the couple publicly displayed "their affection" for their sister-in-law on her 38th birthday. "This time everything was kept private," he added.

The royal family did not share any of the details from Kate Middleton's birthday celebration. They commemorated her 40th birthday with a series of beautiful portraits that will be featured at the National Portrait Gallery.

However, Andersen claimed that the Duchess of Cambridge had a "small affair" with her close friends and family at Anmer Hall. He noted that she "only has a very small circle of friends" and that she continued with her mother Carole Middleton's "interesting" tradition of baking her own birthday cake.

Kate Middleton reportedly also chose to have a "very low-key" party because of the upcoming "big bashes" coming for the royals this year. It is believed that Prince William will have a joint birthday party with Queen Elizabeth II during her Platinum Jubilee celebrations.

"The queen has a big thing planned for [William] and he is going to throw something as well. So, there will be big parties again, if COVID allows anything like that to happen," Andersen explained.

Prince Harry and Meghan Markle are expected to join the Platinum Jubilee celebrations in June. If they do return to the U.K. then this means they will also be there for Prince William's birthday.