Sir Timothy Laurence has tested positive for COVID-19.
The 66-year-old navy officer- who is married to Princess Anne - has tested positive for the virus and is now "following all appropriate rules".
A Buckingham Palace spokesperson told 'Entertainment Tonight': "Princess Anne's husband Vice Admiral Sir Tim Laurence has tested positive for COVID and is following all appropriate rules. Princess Anne is also isolating.”
The royal couple - who has been married since 1992 - are now isolating at their home in Gloucestershire, south-west England, as part of the UK government's coronavirus rules.
Another source told MailOnline: "It's true, COVID is unfortunately on the estate. It means therefore that those in the royal household are having to isolate for the time being."
Timothy's COVID diagnosis was confirmed shortly after Queen Elizabeth cancelled her plans to spend Christmas at her Sandringham estate.
The 95-year-old monarch had intended to follow tradition by spending Christmas at her royal residence in Norfolk, but she recently cancelled those plans amid rising levels of the Omicron variant in the UK.
The Queen - who is the longest-reigning British monarch in history - will instead spend the festive season at Windsor Castle, where she'll be joined by other members of the royal family.
The decision "reflects a precautionary approach", according to Buckingham Palace aides, who confirmed that it was a personal decision taken by the monarch.
At the moment, it's not yet clear which other members of the royal family will join the Queen in Windsor. However, a Buckingham Palace spokesman confirmed that "all appropriate guidelines" would be followed.
The decision to cancel the Queen's trip to Sandringham was taken amid rapidly rising rates of the Omicron variant in the UK.