Prince Harry reportedly decided to attend the King's Coronation a month ago but delayed confirming it publicly as he had some demands for his children.
A former equerry, who is close to both Harry and his brother Prince William, said he was aware of the Duke of Sussex's plans at the beginning of last month.
It has been claimed that one of the main reasons why Harry delayed confirming his attendance was that he wanted some recognition by the Royal Family for his children Archie and Lilibet.
Archie is turning four on May 6 - the same day of the Coronation - and King Charles III was reportedly happy to make a nod to his grandson and raise a glass to him during lunch.
However, it is not clear if Harry will attend the post-Coronation lunch, with claims that he will return to California after the ceremony at Westminster Abbey.
A source told the Mail on Sunday: "The King considered a toast to Archie. But with no member of the Sussex family now due at the lunch, it is highly unlikely he would do in their absence."
While Harry travels to the UK, Meghan Markle will remain in California to celebrate Archie's birthday and sources claimed that Harry will want to travel back home after the ceremony to spend time with his son too.
A royal commentator said Meghan's decision to skip the Coronation was a "brilliant" way for the Sussexes to divide familial and royal responsibilities.
Royal watcher Kristen Meinzer told Insider it makes sense for one parent to celebrate Archie's birthday while the other fulfills his royal obligation.
She said: "I think the decision for Harry to go, and for Meghan to stay home with the children on Archie's birthday is a brilliant way to split the difference.
"As I've said in the past, the primary benefit of attending is the optics; of looking as though they're continuing to do their best on their end — even if the royal family isn't always doing their best on their end.
"But I've always maintained that the Sussexes must also do what's best for their own little family and their own mental health. It sounds like that's what they'll be doing."
