The King has paid £1.5m for repair and restoration costs to Andrew Mountbatten-Windsor's former Royal Lodge home.
Sky News understands the monarch privately made the funds available to his brother.
Earlier on Friday, the Crown Estate announced that the lease on the Windsor property had been officially surrendered.
The King's contribution went towards a £1.8m dilapidations bill. This has been reduced by £302,000 compensation Andrew was entitled to.
The former prince was entitled to compensation because, as per the terms of his lease on the Windsor mansion, he surrendered it within the first 25 years - more than 50 years early.
It is understood Andrew, who had lived at the mansion on the Windsor Estate for more than 20 years, has not personally received a compensation payment.
The former prince left Royal Lodge earlier this year and is now living on the Sandringham Estate.
A spokesperson for the Crown Estate said: "The lease for Royal Lodge has ended and our focus now is firmly on its future use and the opportunities to generate additional financial value for the nation from its early return."
They said the property will now be marketed by two agents for its proposed future use.
Andrew moved out of Royal Lodge in February as part of a permanent move to Norfolk.
Last October, Buckingham Palace said that notice had been served for Andrew to surrender his lease at the Royal Lodge, and the King initiated the "formal process" to remove his brother's titles and honours.
It came after the US Department of Justice released files relating to paedophile financier Jeffrey Epstein, which contained allegations made against Andrew by one of the billionaire's victims.
Andrew has always denied any wrongdoing.
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The official surrendering of the Royal Lodge lease comes a day after the High Court heard Andrew and Thames Valley Police agreed that raids of two of the former prince's properties were unlawful.
Andrew launched a legal challenge to quash the warrants - issued by an Old Bailey judge on 18 February last year - which allowed police to raid Andrew's residence on the Sandringham estate and Royal Lodge.
Andrew was arrested the following day, on his 66th birthday, on suspicion of misconduct in public office following allegations he shared sensitive information with Jeffrey Epstein during his time as the UK's trade envoy.
The criminal investigation into the former Duke of York is ongoing, while further legal proceedings will decide whether police can keep hold of evidence seized during the searches.
A National Audit Office (NAO) report in June found Andrew received an undisclosed private income from subletting three cottages on his Royal Lodge estate for two decades, while paying a peppercorn rent - usually nominal and as low as £1.
He was entitled to sublet up to three properties on the Royal Lodge estate in Windsor Great Park under the terms of his lease.
No figures have been provided on how much income the properties generated, with the NAO saying the figure was private.
However, royal insiders suggested that Andrew's subletting did not produce a profit because the rate only covered maintenance and running costs.
(c) Sky News 2026: King paid Andrew Mountbatten-Windsor's £1.5m Royal Lodge repair bill

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