Prince William is unable to forgive his brother Prince Harry because they made “unkind, cruel, and unrealistic” remarks about Princess Kate, a royal expert has claimed.

The relationship between the Sussexes and the Prince and Princess of Wales remains strained after the fallout following Harry and Meghan’s departure from the Royal Family.

Claims made by Harry and Meghan in Spare, their Netflix series, and their interviews in recent years have left William “too hurt” to build bridges, according to former BBC royal correspondent Michael Cole.

His comments come as Harry prepares to return to the UK in May for the Invictus Games.

Cole told Times Radio: “Of course his mother, the late Princess of Wales Diana, I can’t help thinking of her because when those boys were young she made them promise to each other that they would always be friends and that they would always love and support each other.

“I hope, maybe, a return to his hometown will make Harry think of his mother’s words, and perhaps start to make amends towards reconciliation with his brother.”

The royal expert added: “There are two chances of that happening, slim, and none. I would put my money on none. I don’t believe Prince William is ready to speak to his brother, the hurt is too deep, it is too real, it is too raw.

“His younger brother Harry has done something which William will find extremely hard to forgive….men don’t like their significant other being insulted.

“I’m afraid Prince Harry and Meghan Markle have said unkind and cruel and unrealistic things and untrue things about the Princess of Wales Kate.

“That will come very hard for William….before Harry was engaged to Meghan, he was very close to Kate. He was always in their apartments at Kensington Palace.

“William I think got a bit fed up of him being so close to his wife, but the three of them couldn’t have been happier together.”

While Harry is unlikely to see William when he returns to the UK, it is a possibility he could meet with his father King Charles as he continues to receive treatment for his cancer.

But royal insiders have claimed that the King may be “too busy” to speak with Harry, as reported by the Telegraph.