"[The Duke and Duchess of Cambridge] are extremely busy at the moment," the royal author told the Daily Mail. "They're moving home, they need to settle their children into new schools. They're very busy taking on so many more engagements for the Queen."
Levin went on to say making amends would be "very difficult and certainly not before [Harry's] memoir comes out because we don't know what he's going to say.
"[Harry's] been very unkind and cruel so far. We have to wait to see what he does - maybe they won't want to see them until all that's out in the open and they know what he says."
Another royal expert, Richard Fitzwilliams, has seconded Levin's claims. He told Femail the Cambridge-Sussex rift is "very deep" and doubts a reunion when the Sussexes return to the UK "probably won't" be seen.
"I suspect that the rift is very deep, the reports are that they probably won't," he said.
While the Sussexes, who have made a new home in Montecito, California, have returned to the UK twice this year, it is claimed they did not meet with the Cambridges on either visit.
According to the Daily Mail, William and Harry have not spoken to each other "face-to-face" since the unveiling of their mother Princess Diana's statue in July last year.
The Sussexes will travel to the UK for the One Young World Summit, to be held in Manchester. It is understood Meghan will give the keynote address at the opening ceremony.
The next day the pair will head to Germany to commemorate a year until the Invictus Games in Dusseldorf.
From here they return to the UK for the WellChild Awards in London, where Prince Harry will deliver a speech.
