Kate Middleton could step in at the unveiling of Princess Diana's statue if Prince Harry is unable to make it.
The Duke of Sussex, 36, hopes to fly back to the UK for the poignant event on July 1 on what would have been his mum's 60th birthday.
Meghan Markle, however, is poised to give birth to a new daughter, Harry may be forced to miss the unveiling at Kensington Palace.
Royal observers say Kate could now fill in to support her husband Prince William at the event.
The Mirror Royal Editor Russell Myers told the Pod Save The Queen podcast: "Meghan is about to give birth, one would presume - they said early summer - so whether he will, whether he won't.
"Will there be an appetite for him to keep on criticising his family in that way?
"He's potentially going to be standing shoulder-to-shoulder with his brother when they unveil the Princess Diana statue."
He added: "That could make it very, very uncomfortable, [although] whether he comes over is a matter for debate at the moment because they are expecting their second child.
"Maybe Kate will step in to not have William do it on his own."
It had been hoped Harry's return to the UK could could help repair the “deteriorating” relationship with his brother Prince William.
But his return has been in “serious doubt” for weeks after a rift between the family intensified, royal experts have claimed.
Harry's recent attacks on his family in interviews may make the reunion "very uncomfortable".
It was previously claimed that Harry would return to the UK to unveil the Princess Diana statue after chatting with his brother at Prince Philip's funeral.
The brothers have had frosty relations since Harry sensationally moved to the US and stepped back from royal life in 2020.
Their relationship was strained further after Harry and Meghan's bombshell interview with Oprah earlier this year.
But after a solemn reunion at Prince Philip's funeral, the door was opened for further reconciliation, it was said.
Harry is poised to have his HRH title "expunged" from notices at a new royal fashion exhibition featuring his mother 's wedding dress.
Placards at the Kensington Palace exhibit last week described dresses worn by Diana as "Lent by HRH the Duke of Cambridge and HRH the Duke of Sussex"
The Royal Collection Trust, which oversaw the loan of the gowns, had said the labels "were incorrect and will be updated" citing an "administrative error'.
Under a historic deal struck at Sandringham last year, the Duke and Duchess of Sussex were allowed to keep their HRH titles but never use them.
Royal experts have suggested the decision to remove Harry's HRH title from signs at the exhibit, called Royal Style in the Making, is a sign of the sensitivity over Harry and Meghan sudden departure from royal life.
