@milee30 I think you meant Will and Kate (as Harry never attended university), but with their grades of AAC and AAB respectively, they would have had a shot at Oxbridge at the time they applied to university, especially William.
Will’s predecessors could get into Cambridge with grades of CCD (Edward) and BC (Charles). See: https://www.telegraph.co.uk/news/uknews/1531553/The-family-qualifications.html .
Even well connected individuals, e.g. the journalist Toby Young, in the UK can seep through the grade requirements system for Oxbridge:
God loves a trier and high-ranking media execs love a chancer. Certainly some kind of all-powerful deity must be looking out for the Tobys. I’m not saying they always land on their feet but to get into Cambridge University I needed 11 A-grade GCSEs, four A-grade A-levels, plus a Ucas statement stuffed with enough extra-credit activities to make Malala Yousafzai look like a slouch. To get into Oxford, Young needed, by his own admission, two Bs and a C at A-level, plus a phone call from his dad. Who was Toby Young’s dad? Baron Young of Dartington, a pioneering sociologist who also — you’ll enjoy this — happened to coin the word “meritocracy”.
https://www.standard.co.uk/comment/comment/a-wellconnected-ambitious-blowhard-toby-young-is-just-what-education-doesn-t-need-a3731921.html