Harry's old friend Charlie van Straubenzee is marrying Daisy Jenks in Surrey and, according to reports, the royal couple will be among the guests.
The groom may have paid the royal the ultimate compliment by asking him to be his best man.
It may be enjoyed as a double celebration as it is also Meghan's 37th birthday and her first as a member of the Royal Family.
Charlie was an usher at Harry's recent wedding, along with older brother Thomas van Straubenzee.
The Duke and Duchess of Cambridge are also rumoured to be invited to the couple's big day as William is good friends with the van Straubenzee brothers, with Thomas a godfather to his daughter Princess Charlotte.
Last year Harry reportedly whisked Meghan away for a romantic break in Africa to mark her 36th birthday, flying to Botswana.
She married Harry during a ceremony watched by an estimated television audience of hundreds of millions, and it was praised for combining tradition with modernity and diversity.
Sir Elton John, who performed at the wedding reception, described it as a memorable event and said: "To have a black gospel choir, a multiracial bride, a black cellist, who was wonderful, a preacher - it felt like a party, and it felt like progress had been made.
"Thank God, thank God."
Sir Elton added: "I think the Queen had a lot to do with it. I think she's been magnificent. It was a wonderful thing to be at."
Harry and Meghan were able to enjoy their honeymoon without being discovered, jetting off to their undisclosed destination soon after they wed on May 19.
They live in a property in the grounds of Kensington Palace but are rumoured to also have a country bolt-hole somewhere in the Cotswolds.