Britain's Prince William contracted COVID-19 in April at a similar time to his father, Prince Charles, the BBC reported citing royal sources.
The report came after newspaper The Sun carried an article exclusively revealing details about the prince's secret battle with the disease.
Prince William was treated by palace doctors and followed government guidelines by isolating himself at the family home, Anmer Hall in Norfolk.
"There were important things going on and I didn't want to worry anyone," William told one observer at an engagement, according to the report in The Sun.
"William was hit pretty hard by the virus – it really knocked him for six. At one stage he was struggling to breathe, so obviously everyone around him was pretty panicked," a source told the newspaper.
Prince Charles' office said on March 25 that Charles had tested positive for the coronavirus. He self-isolated at his residence in Scotland for seven days with mild symptoms.
Kensington Palace and the office of Prince William are yet to comment on the reports.
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UK's Prince Charles tests positive for coronavirus
The UK has so far registered 1,034,914 confirmed COVID-19 cases with 46,717 deaths.
Last week, British Prime Minister Boris Johnson announced new restrictions across England would kick in after midnight on Thursday morning and last until December 2.
All but essential shops, along with pubs and restaurants, will close from Thursday and people have been told to stay at home and not meet up with friends and family.
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England will have month-long national lockdown, announces Boris Johnson
(Cover: Britain's Prince William leaves the Lindo Wing of St Mary's Hospital after his wife Catherine, the Duchess of Cambridge, gave birth to a son, in London, April 23, 2018. /Reuters )