Angela Levin has expressed her concerns for Prince William, following the recent health updates for Princess Kate and King Charles.
The Princess of Wales is currently recovering at Adelaide Cottage following planned abdominal surgery at The London Clinic.
On Monday, following treatment at the same hospital for a "benign enlarged prostate", King Charles announced he had been diagnosed with "a form of cancer".
The monarch has said he is "wholly positive" about his diagnosis, and will begin "scheduled regular" treatment immediately.
Angela Levin says Prince William is facing a 'difficult time'
PA / GB News
Both the King and Princess of Wales have stepped down from public-facing duties for the foreseeable future, inflicting pressure on Prince William and Queen Camilla to step up duties in their absence.
Prince Harry is also expected to fly to the UK in the next 48 hours to be with the Royal Family. He is travelling alone, leaving wife Meghan Markle and children Archie and Lilibet at home in California.
As Prince William cares for Princess Kate and looks after their three children, Prince George, Princess Charlotte and Prince Louis, royal biographer Angela Levin highlighted the "difficult time" the Prince now faces as he juggles both his royal duties and personal duties as a husband, son and father.
Speaking to GB News, Angela Levin said the Prince will have a "hard time" managing his care for the Princess of Wales as well as taking on duties on behalf of her and the King.
Angela Levin says a lot of the Royal Family's work is now 'leaning on' Prince William
GB News
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Discussing Prince Harry's return amid the Royal Family's health concerns, Levin said William has "got used to Harry being rude, unkind and attacking his wife".
She added: "It's very hard for him. He doesn't want to have anything to do with Harry at the moment and you can't blame him, because he's been so rude and told untruths about both William and Catherine.
"I don't know how you completely can change that. It's difficult, isn't it? It's difficult to completely turn over a relationship and forget all the past. I don't think people can do that."
Host Isabel Webster agreed with Levin, and claimed Prince William may be feeling "incredibly lonely" right now.
Princess Kate is recovering at home following her abdominal surgery
PA
Isabel highlighted: "This is somebody who's estranged from his brother, he lost his mother in tragic circumstances, recently lost his granny, who was one of the few who understood the responsibility he faces.
"And one of his uncles is disgraced, now his father and wife both unwell."
Levin responded: "Harry said to me when I was writing his biography that he and William couldn't be closer, we trust each other totally.
"We are together. We have the most amazing relationship because we've had the same experiences, terrible, difficult experiences. But now that's not the case."