Prince Harry, Meghan's daughter celebrates 1st birthday in UK amid possible 1st meeting with Queen Elizabeth II

Lilibet "Lili" Diana Mountbatten-Windsor, the youngest child of Prince Harry and Meghan, is celebrating her 1st birthday in the U.K.

Lili, who turns 1 on Saturday, made her first trip to the U.K. this week with her parents and older brother Archie, 3, to celebrate her great-grandmother Queen Elizabeth II's Platinum Jubilee, marking 70 years on the throne.

The trip to the U.K. also presented Lili with the opportunity to possibly meet her namesake, according to ABC News royal contributor Omid Scobie.

Lilibet, Lili's full given name, is the family nickname of the 96-year-old queen.

"This trip has not only been an opportunity for Harry and Meghan to celebrate the queen’s Platinum Jubilee, but also a chance for the queen to meet their daughter," said Scobie. "Yesterday, after Trooping the Color, would have been the first opportunity for the queen to meet Lilibet, as they both returned to Windsor following the parade."

The queen's official Twitter account posted happy birthday wishes on Saturday.

"Wishing Lilibet a very Happy 1st Birthday!," read the tweet, accompanied by an image of a red balloon.

Lili was born in California, where the Sussexes moved in 2020 after stepping down from their roles as senior working royals. She is the first senior royal baby born in the U.S. and the first great-grandchild of the queen to be born outside of the U.K.

Neither Lili nor Archie, who was born in the U.K., are believed to have seen the queen in-person in the past two years.

"Despite everything that has happened, the relationship between the Sussexes and the Queen has remained warm and close," said Scobie. "Introducing her to Lilibet will no doubt be one of the highlights of the Sussexes' time here in England and a moment the queen has been looking forward to."

The queen has been spending much of her time during the four-day jubilee holiday at Windsor Castle, which is close to Harry and Meghan's home base in the U.K., Frogmore Cottage.

On Saturday, Lili's birthday, Harry and Megan plan to spend the day "together privately as a family," according to a spokesperson for the Sussexes.

Harry and Meghan's only public appearance so far during the jubilee was Friday morning when they joined royal family members at St. Paul's Cathedral in London for a National Service of Thanksgiving in honor of the queen. The service, which the queen did not attend, was the Sussexes' first public appearance at a royal event in two years.

On Thursday, Harry and Meghan privately attended Trooping the Color, watching the parade and fly-past with other royal family members from an office in Buckingham Palace.

It remains unclear who all from the royal family the Sussexes are spending time with during their visit to the U.K.

Harry's brother, Prince William, and his wife Kate, the Duke and Duchess of Cambridge, are not known to have met Lili since her birth.

William and Kate are the parents of Archie and Lili's only cousins, Prince George, Princess Charlotte and Prince Louis.

Harry has been public over the past two years about having a strained relationship with his brother. While both brothers and their wives attended Friday's church service, they were not seen publicly interacting.

Scobie was optimistic that a meeting would happen between the cousins and aunts and uncles, adding, "I would say there are still opportunities in the days ahead."

"I think everyone has really put any difficulties to one side to really make sure that all attention remains focused on the queen and that the environment that they're all in is really positive," he said, adding that he and other royal experts are watching to see how Harry and Meghan are "getting on with their family members."

Robert Jobson, also an ABC News royal contributor, countered, saying he believes there is "not a chance" Archie and Lili will spend much time with other relatives, including George, Charlotte and Louis.

"They had one job to do, which was to introduce Lilibet to the queen," he said of Harry and Meghan. "That’s done. There’s no way they're playing with the cousins."

Following Friday's church service, William and Kate attended a reception with other royal family members while Harry and Meghan returned to Frogmore Cottage, according to reports.