Aside from the fact you now know he does NOT have prostate cancer, it can be an aggressive serious disease-it kills 10,000 men a year and is a bloody awful way to go. Your uncle was lucky, and you should get regularly PSA check-ups from age 45 since it's in your family and you seem to have a very blasé attitude towards it. My dad certainly didn't live 20 years from diagnosis with it, many men do but there are different types and some are far more aggressive than others. I have huge regrets over not taking my dads cancer seriously and showing enough support or worry til we knew it was stage 4 because of this type of attitude that "oh prostate cancer never kills."
I hope whatever it is King Charles has it's been in caught in the early stages. It's a very worrying time and my heart goes out to all the Royal family.