Charles’s younger son Harry and his American wife Meghan quit royal duties in 2020 and have since unleashed a string of barbed attacks on the monarchy.
Andrew, the king’s eldest brother, has been frozen out over his past association with the disgraced late US financier Jeffrey Epstein and a related sexual abuse allegation which was settled out of court.
Harry, 38, the Duke of Sussex, and 63-year-old Andrew, the Duke of York, will attend the coronation service at London’s Westminster Abbey but will not perform any duties.
The pair will also be absent from the public procession behind the Gold State Coach carrying the newly crowned king from the abbey back to Buckingham Palace after the ceremony.
But they may yet appear on the palace balcony.
Harry is fifth in line to the throne, following his brother Prince William, and William’s three children — Prince George, Princess Charlotte and Prince Louis of Wales.
Andrew is eighth in line, coming after Harry and his children — Prince Archie and Princess Lilibet of Sussex.
After finally deciding to attend, Harry’s every move will be heavily scrutinised. He rejoins his family for the first time since subjecting them to a torrent of stinging criticism in his memoir “Spare” and in a series of television interviews.
Meghan has remained in California with the children, thereby avoiding potentially awkward interactions with her in-laws.
At the 1953 coronation of Queen Elizabeth II, the royal dukes each paid personal homage and allegiance to the monarch, in a public vow of loyalty.
They pledged to “become your liege man of life and limb, and of earthly worship; and faith and truth I will bear unto you, to live and die, against all manner of folks. So help me God.”
But this time, only William, the heir to the throne, will speak “the words of fealty” and pay “the homage of royal blood”, as the coronation liturgy calls it — sparing Harry from having to kneel before his father.
Buckingham Palace has not said whether Harry and Andrew will or will not appear on the palace balcony following the ceremony.
At Queen Elizabeth II’s Platinum Jubilee celebrations last June for her 70 years on the throne, the balcony appearance was restricted to working royals only.
But her coronation in 1953 featured multiple balcony appearances, so Harry and Andrew might potentially appear among a wider royal family gathering.
Saturday marks Archie’s fourth birthday, so Harry might make a swift exit back to his home in California.
Andrew’s links with Epstein — boyfriend of the prince’s friend Ghislaine Maxwell — came back to haunt him.
A US woman, Virginia Giuffre, said she was pressured to have sex with Andrew when she was 17 after being delivered by Epstein, who was convicted in 2008 of procuring a child for prostitution.
Andrew denied the allegations in a November 2019 BBC interview that nonetheless went down badly.
Within days, he stepped back from his patronages and in May 2020 he permanently resigned from all public roles.
The case was settled out of court in February 2022, with Giuffre accepting a donation to her charity and no admission of liability from Andrew.
Andrew took part in events surrounding Queen Elizabeth II’s funeral but, beyond mourning his mother, Charles has shown no sign of allowing him a return to public life.