The Prince of Wales's godfather, King Constantine II, remains in critical condition following a stroke.
Greek City Times reported King Constantine II, 82, has been in ICU for several days at a private hospital.
The report further claims that Prince William shares an extremely close bond with his godfather.
Before suffering a stroke, King Constantine, known as the last king of Greece, was hospitalised with Covid earlier this month.
King Constantine II reigned from March 1964 until the abolition of the Greek monarchy in June 1973.
Prince William, the heir to the throne, received the distressing news as Prince Harry was set to discuss his memoir in highly anticipated television interviews Sunday after the controversy caused by details of the book´s explosive revelations about royal rifts.