Prince Harry and Prince William reportedly "quarrelled" at Prince Philip's funeral
The brothers will reunite later this week.
According to reports, Prince Harry and Prince William weren't on the best terms at the funeral of their grandfather earlier this year.
Royal historian Robert Lacey has alleged that an argument broke out between the brothers at Prince Philip's funeral.
In an article for the Daily Mail, Lacey reported that the princes were "at each other's throats as fiercely as ever".
A friend of the royals' told Mr Lacey: "The rage and anger between those two has grown so incredibly deep."
The source added that "too many harsh and wounding things have been said".
Prince Harry and Prince William are expected to reunite this week at a ceremony unveiling a statue of their mother, Princess Diana. The event marks what would have been Diana's 60th birthday on 1 July.
Reports that the brothers have been at odds have gained traction following Harry and Meghan's interview with Oprah Winfrey earlier this year.
Afterwards, Prince William told the press that he hadn't spoken to Harry about it, but said that he was planning to. He also said that they are "very much not a racist family".
William's statement came after Meghan alleged that there were "conversations" about the colour of Archie's skin before he was born.
Harry has also spoken about his experience growing up in the royal family, and how he wishes to protect his children from that pain.
During his appearance on The Armchair Expert Podcast, Harry said: "I don't think we should be pointing the finger or blaming anybody but certainly when it comes to parenting, if I've experienced some form of pain or suffering because of the pain or suffering that perhaps my father or my parents suffered. I'm going to make sure I break that cycle so that I don't pass it on."