Royal author Katie Nicholl said Eugenie and her husband Jack Brooksbank were in a position to help as they have been close to Harry and Meghan Markle since the early days of their romance.
Ms Nicholl told OK! magazine: “They were close from the start, and I think they recognise that Harry has been ostracised by some members of the family.
“I think they also see they’re in a position to try and act as peacemakers and defuse the situation, which they tried to do at the Duke of Edinburgh’s funeral.”
Ms Nicholl added that Eugenie and her sister Princess Beatrice were reluctant to take sides between the Sussexes and the rest of the royals.
The royal expert said: “They just want it to be like the good old days when all the cousins got on well and had fun together.”
Eugenie became the first member of the Royal Family to make a public visit to Harry in California earlier this month.
The cousins were seen attending the Super Bowl at the SoFi Stadium in Los Angeles.
Eugenie and Jack are also living at the Sussexes’ former Windsor home Frogmore Cottage with their son August.
Harry is understood to have stayed with them during his two UK visits since Megxit.
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“It was Eugenie who helped set up Harry and Cressida.
“She refuses to abandon him. She is a very loyal lady. She is not one for taking sides.
“With Harry’s communication with the family limited Eugenie could be his one conduit to a reconciliation. But that seems a long way off.
“She is close to the Queen and to Harry and Meghan and their meeting shows he is not completely out in the cold.”
Royal expert Phil Dampier also suggested Eugenie could be an “intermediary” between Harry and the royals.
He told the Telegraph: “They’ve always got on very well and been very close.
“If there is going to be an emissary, or an intermediary, between Harry and the Royal Family back home, she could well fit the bill.
“I’m sure when they met in LA, they would have talked about the situation – and I’m sure she’ll be trying to smooth things over.
“She could be one of the ways whereby tentative steps could be taken to try and heal the rift.”