The Prince of Wales was insistent that his in-laws Carole and Michael Middleton be invited to the King's coronation last May, a new royal book claims.
According to The Mirror, author Robert Hardman writes in his new publication, Charles III: The Inside Story that Prince William made a "direct request" that his wife Kate's parents be in attendance and given prominent seats inside Westminster Abbey.
The newspaper reports that the author points out the major differences between Queen Elizabeth II's 1953 coronation and that of King Charles.
"Such are the shifting sand that, seventy years on, the Middletons outnumber the Mountbattens four to one," he writes.
Over 8,000 guests witnessed the moment the late Queen was crowned, in comparison to the 2,200-strong congregation at Charles' coronation.
The only representative from Prince Philip's side of the family was long-time friend and wife of the King's second cousin, Penelope Knatchbull, Countess of Burma.
Lady Pamela Hicks, one of the late Queen's bridesmaids and ladies-in-waiting, was among those to miss out on an invitation, her daughter India Hicks revealed ahead of the ceremony.
But in an Instagram post, India added that her mother Lady Pamela was not offended at all and agreed: 'How very, very sensible."
Businesswoman Carole and former flight dispatcher, Michael, were captured arriving at Westminster Abbey for the ceremony, alongside their children, Pippa Matthews and James Middleton.
Pippa was not joined by her husband, James Matthews, and made a solo appearance with her younger brother, James, whose wife Alizee Thevenet also did not attend.
The Middletons reside in Bucklebury, Berkshire and William is said to have had a close bond with Kate's family since they first met at St Andrews University over 20 years ago.
In their engagement interview in 2010, the Prince said: "Kate's got a very, very close family. I get on really well with them and I'm very lucky that they've been so supportive. Mike and Carole have been really loving and caring and really fun and have been really welcoming towards me so I've felt really a part of the family and I hope that Kate's felt the same with my family."
Carole and Michael are grandparents to William and Kate's three children – Prince George, ten, Princess Charlotte, eight, and five-year-old Prince Louis.
Pippa also has three children with husband James, Arthur, Grace and Rose, while James and Alizee welcomed their son Inigo in autumn last year.