The Duke and Duchess of Sussex recently returned to the U.K. for the Jubilee, staying at their old home in Frogmore Cottage, where they recently renewed a lease. The queen also met her great-grandaughter for the first time on Thursday.
A source close to the family tells ET that Meghan and Harry celebrated their daughter's big day at Frogmore with several relatives, including Princess Anne's children, Zara Tindall and Peter Phillips, along with their spouses and children.
The source added that Peter has been very close to Prince William and Prince Harry ever since Princess Diana's death in 1997, when the queen asked Peter to join the boys in Balmoral.
Though the Duke and Duchess of Cambridge did not attend Lilibet's party, ET previously reported that their absence was "no intended slight." Several members of the royal family -- including Will and Kate -- all traveled to different parts of the U.K. on Saturday to visit those celebrating the Jubilee. The source was adamant the events were not planned to avoid Lilibet's birthday at home.
The party on Saturday was an opportunity for the young children who are close in age to spend some time together, the source noted, adding that it was low-key and relaxed with birthday cake for all the kids to enjoy.