Inside Prince Archie's 'Low-Key' 4th Birthday Plans on Coronation Day

Plans are in place for Prince Archie's upcoming birthday party.

King Charles' coronation on May 6 falls on his grandson's birthday. While Prince Harry will be in the U.K. to attend his father's crowning ceremony, Meghan Markle will remain in California with their two children -- and celebrate Archie turning 4.

"It's going to be a low-key party at home," a source tells PEOPLE in this week's cover story. "They'll have friends around them and Meghan's mom, Doria [Ragland]. Meghan will definitely have support that weekend."

Of course, Archie's little sister, Princess Lilibet, will also be part of the festivities.

"They are so sweet together.

Archie loves Lili. He's such a sweet boy. When she's not around, he asks, 'Where's Lili?' " the source adds.

Prince Archie and Princess Lilibet were last in the U.K. during Queen Elizabeth's Platinum Jubilee celebrations in June 2022.

The significant trip was Princess Lili's first visit to the U.K., as she was born in California on June 4, 2021, and had yet to visit her dad's homeland. Archie was born in the U.K. on May 6, 2019, but hadn't been back since late 2019.

A royal source told PEOPLE at the time that it was a "fantastic visit." The trip allowed Lili to meet her grandfather, then known as Prince Charles, and her great-grandmother, Queen Elizabeth, for the first time. Prince Harry and Meghan named their daughter in the Queen's honor, as Lilibet was her childhood nickname.

"The prince was delighted to see his grandson and meet his granddaughter for the first time," the source said, adding that it was "very emotional" and a "wonderful thing" for Charles to meet Lili.

During the Duke and Duchess of Sussex's time in the U.K. in June, they held a small birthday party for Lili, who turned 1 during the trip. The couple, who relocated to Meghan's home state of California after stepping back from their royal roles in 2020, invited close friends and family to gather for a "casual, intimate backyard picnic" at Frogmore Cottage, a spokesperson said.

The couple also released a new photo of their daughter in honor of her milestone birthday, revealing her red hair -- which she inherited from dad Harry!

Fans got another glimpse of the festivities in the Netflix docuseries Harry & Meghan, which aired in December 2022.

The Duke and Duchess of Sussex shared intimate family photos throughout the six-episode series, including from Lili's birthday party.

Prince Harry and Meghan Markle. Michael M.

Santiago/Getty

Can't get enough of PEOPLE's Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more!

In March, Prince Harry and Meghan revealed that Princess Lilibet had been christened in California.

The statement was significant, as it marked the first time that the couple referred to their children's royal titles.

Upon the death of Queen Elizabeth in September, Harry's father became King Charles -- and as grandchildren of the monarch, Archie and Lili were afforded the titles of prince and princess.

"The children's titles have been a birthright since their grandfather became monarch," a spokesperson for the Duke and Duchess of Sussex told PEOPLE. "This matter has been settled for some time in alignment with Buckingham Palace."