However, Harry and Meghan's secret deal with Eugenie and Jack was reportedly not discussed with senior members of the family, including the Queen.
“Senior royals were initially blindsided by the idea for Harry and Meg to let Eugenie and Jack move in," a source told The Sun.
“Obviously the Queen was told after the couples had spoken about the plan."
The source added: “But it is very much a deal done between Harry, Meghan, Eugenie and Jack. There is a close bond between them."
A Buckingham Palace spokesperson told the newspaper: “Frogmore Cottage is the private residence of the Duke and Duchess of Sussex and as such any arrangements are a matter for them.”
Harry and his cousin Eugenie share a close relationship and have done for many years since they were children.
Princess Eugenie even set Harry up with his last serious girlfriend before Meghan, Cressida Bonas.
"Harry had always confided in his cousin when it came to the women in his life," royal writers Carolyn Durand and Omid Scobie wrote in their biography, Finding Freedom.
"Not only did he trust her implicitly, but friends say that she gives great advice and has always been 'beyond wise' for her years. It's not surprising, then, that Eugenie was one of the first in the family to know about his relationship with Meghan."
The book added that: "Eugenie who'd long wanted to see her cousin settle down and be happy, told friends she loved Meghan and thought she was 'just the tonic' for Harry."
However, the youngest daughter of Prince Andrew and Sarah Ferguson was reportedly not pleased that Harry and Meghan decided to announce their pregnancy news to the family at her October 2018 nuptials.
"It did not go down particularly well with Eugenie, who, a source said, told friends she felt the couple should have waited to share the news," an extract from Finding Freedom reads.