Prince Andrew's past may contain more "unexploded bombs", Palace aides fear.
Courtiers in Buckingham Palace fear that the King may face further questions over his brother's past.
The Duke of York was forced to give up his role as a working royal in 2019 following his disastrous Newsnight interview on his links to Jeffrey Epstein and has faced repeated media attention on the topic ever since.
Aides fear that there may be more stories to come from the 63-year-old's associations with the late convicted paedophile.
Prince Andrew has left aides fearing there's 'more to come out'
Epstein was found dead in a New York jail in 2019.
"It feels like more stuff is going to come out," a source told The Sunday Times.
"There are still unexploded bombs."
The insider added that the King has no desire to bring his brother "out of the freezer", with the Duke largely sidelined from public life.
Andrew has only been seen on rare occasions in recent years, only appearing alongside other members of the Royal Family at events such as the Queen's funeral and Charle's Coronation.
He has been only mildly more visible than Prince Harry and Meghan Markle in their involvement in royal life.
However, officials close to the King suggest that Andrew is seen as greater issue than the bickering from Harry and his wife.
One source said: "Andrew is more of a long-term problem than Harry and Meghan."
King Charles is said to see Andrew as a bigger problem than Harry and Meghan
Another added of the King's attitude to the attacks from the Duke and Duchess of Sussex: "He has done the right thing to rise above it and carry on with the work of the monarchy, which provides a welcome and stark contrast to what happens on the west coast of America.
"It’s all very sad, but it also mirrors what happens in a lot of families, so it humanises him.
"What’s clear is the side the public has come down on, and that’s reassuring to him."