Princess Lilibet's second birthday was this past Sunday, and apparently Prince Harry "warned" Lili's grandfather, King Charles, what to get her for the occasion, OK reported.

The King apparently intended to give his youngest grandson the perfect gift for his big day, and according to one source, Prince Charles "had his aides look for a custom-made cubby house, similar to the one the Queen and Princess Margaret had when they were girls."

"He wants to give Lili something that she will use and that will be hers," the source said. 'It would be the ultimate surprise. (We still don't know if Lili received the gift on Sunday.)

But Harry had an opinion about the gift: Charles was going to give Lili an unforgettable present, but "Harry warned Charles not to be too extravagant," sources Says.

Charles and Harry's strained relationship has been on the mend since the two met briefly in March when Harry was in England for a court appearance. (After that, the King finally started taking phone calls from his son again," a source said, adding that there have been several phone calls between the two since then. Harry then attended Prince Charles' coronation on May 6, while his wife Meghan Markle and sons Prince Archie and Lili remained at their home in Montecito, California.

May 6 was also Archie's fourth birthday, and the king did not forget the occasion, toasting "those who were not there" after the ceremony, including a special Happy Birthday to Archie "wherever he was." One insider called it "a very sweet moment."