Harry and Meghan staying at a palace with their children would signal a major thawing in the relationship between the King and his son, and offer the perfect opportunity for Charles to reconnect with the young royals.
It is four years since Archie, seven, and Lilibet, five, last saw their grandfather the King in person during Queen Elizabeth II's Platinum Jubilee celebrations in 2022.
The Sussexes are expected to travel from their Californian home to the UK next month to attend celebrations marking the one-year countdown to Harry's Invictus Games hosted by Birmingham, with the duke also due to attend events with WellChild and Scotty's Little Soldiers, charities he supports.
Harry has faced a protracted legal battle with the Home Office over the security arrangements for him and his family when in the UK after his level of protection changed when he stepped down as a working royal in 2020.
Security worries for his family have been cited by the duke as a reason he could not bring them to the UK but it appears his concerns have been mitigated, with reports claiming the Sussexes were given assurances.
But sources have stressed all matters of security are issues for the Home Office to decide and the King does not play a role in the process and has not made any private undertakings.
Harry and Meghan do not have a permanent UK home after they were asked to vacate their Windsor residence Frogmore Cottage, a gift from the late Queen, in 2023 just weeks after the duke's damning memoir Spare was released.
It is understood the duke and his family have been offered accommodation on the royal estate for their up-coming visit, but have yet to respond. Buckingham Palace was suggested as a place they could use during previous potential trips but the gesture was not taken up.
The trip comes after Harry met Charles, who is still undergoing treatment for cancer, last September for the first time for 19 months.
When the duke lost a Court of Appeal challenge against the Home Office last year, over his UK security arrangements, he gave a BBC interview in which he expressed hopes of a reconciliation with his family, revealing Charles would not speak to him because of his court battle over his security.
Harry added he "can't see a world in which I would be bringing my wife and children back to the UK".
But he later wrote to Home Secretary Shabana Mahmood and submitted a formal request for a risk assessment to the Executive Committee for the Protection of Royalty and Public Figures (Ravec), a body overseen by the Home Office which originally changed the degree of his UK protection.
A report by the Sun followed stating the duke's security arrangements were being reviewed.
The duke, who stepped down from the working monarchy in 2020, has levelled a barrage of accusations at the King, his stepmother the Queen, brother the Prince of Wales and sister-in-law the Princess of Wales in his Oprah interview, Netflix documentary, interviews and his autobiography Spare since moving to the US.
Harry previously claimed Charles was jealous of Meghan and Kate, did not hug him when he told him his mother Diana, Princess of Wales had died, and said he believed the King was "never made" for single parenthood, but "to be fair, he tried".
Charles, according to the duke, pleaded with his sons during a tense meeting after the Duke of Edinburgh's funeral: "Please, boys. Don't make my final years a misery."
Harry, who claimed in his memoir that William physically attacked him and pushed him into a dog bowl, remains estranged from his brother.
The duke's spokesperson and Buckingham Palace have yet to comment.
