A new book says Prince William cut his household from his brother after an angry conversation over Meghan Markle.
Robert Lacey's book Battle of the Brothers uncovers what may have happened during the brothers' falling out.
A source close to the Sussexes said "William threw Harry out", according Lacey.
It's understood this happened after staff claimed Meghan "played the victim, but was a bully" and William told his friend he thought she had an "agenda". The book also states William told his brother to take things slow.
Staff are quoted in the book saying Meghan "played the victim, but was a bully" and treated staff poorly.
Both Harry and Meghan have denied any claims of bullying.
William was left feeling "hurt" and "betrayed" by the rift, telling a friend his wife Kate "had been wary of Meghan from the start".
The book also said he felt Meghan was "stealing his beloved brother away from him" and that she was "hostile" towards the Firm, planning to leave from the very beginning.
Lacey's book also quotes a Kensington Palace courtier who said: "Meghan portrayed herself as the victim, but she was the bully. People felt run over by her. They thought she was a complete narcissist and sociopath — basically unhinged."
William had to put the monarchy ahead of his brother, and stopped seeing it as his duty to protect the younger sibling, while Harry was equally angered his brother believed the accusations being fired at his wife, the book claimed.
In the past it was thought Harry chose to split the households however the book says it was Prince William's decision.
Lacey said the households started to drift apart after an argument in autumn 2018.
In the book the author said he believes William thought that Meghan had an "agenda" and voiced his concerns before the couple's engagement.
However an argument after Harry and Meghan's Australian trip in 2018 sealed William's decision to split to two households.
During the Oprah interview, Harry cited that 2018 trip as the moment "the family got to see how incredible she is at the job".
While comparing her and the alleged treatment she received by the royal family to his mother Princess Diana.
The brotherly rift was started by an official email claiming Meghan was bullying staff which was sent by Jason Knauf, communications secretary to the Cambridges and Sussexes.
Since the allegations, a spokesperson for the Sussexes said the couple are the target of a smear campaign, and denied allegations of bullying.
The author also touched on that infamous Oprah interview, with Lacey saying Prince Harry claimed the brothers' falling out began because the Firm was jealous his wife Meghan was so good with people, something he said echoed his mother Princess Diana's treatment.
However, the brothers were no longer on speaking terms before Harry and Meghan left for Australia, the book states, adding that it was bullying allegations that sparked a brutal row.
"I overheard a conversation between Harry and one of his top aides. Harry was screaming down the phone. Team Sussex was a really toxic environment," one staffer told Lacey.