"William was quite concerned that the relationship had moved so quickly," Nicholl explained in the documentary. "And being close to Harry, probably the only person close enough to say to Harry, 'This seems to be moving quickly, are you sure?'"
She continued: "I think what was meant as well-intended brotherly advice just riled Harry. Harry is hugely protective of Meghan. He saw that as criticism. He interpreted that as his brother not really being behind this marriage, this union, and I don’t think things have been quite right ever since."
Harry's recent speech explaining the couple's decision to step back as senior members of the royal family was the first time either brother had confirmed a rift between the pair.
"Part of this role, part of this job, this family, being under the pressure which it's under, inevitably stuff happens," Prince Harry told interviewer Tom Bradby. "But we are brothers. We will always be brothers. We are certainly on different paths at the moment, but I will always be there for him, and as I know he will always be there for me.
Despite this being the first-ever public mention of their feud, the Duke of Sussex suggested some of the tabloid coverage of the rift was overblown. "I love him dearly and you know, the majority of the stuff is probably — well, the majority of the stuff is created out of nothing. But as brothers, you have good days and you have bad days," Prince Harry said.
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