Jane and Charles Blount both responded to recent claims from ex-pop impresario Pete Waterman of too many modern pop stars being university educated.
In an email to BBC Radio 4's Today programme, Jane said: "I was most interested to hear Pete Waterman's thoughts on public school rock stars. His attitude is reflected by most of the critics in UK.
"My son, who is hugely appreciated worldwide, receives harsh criticism here and we have, rather sadly, been aware that it is because of his background. We are relieved that on the whole James's fanbase take no notice of the critics."
Chris added to The Guardian: "It's ridiculous. The key question is not about background; it's to do with their talent. It's like racism or anything else: people should be judged on their talent, not their background."