I sometimes wonder if excluding the Yorks is because Charles feels he was a bit hard done by compared to Andrew?
His mother became queen when he was very young and, as she was so young herself, all her focus had to be on the role of monarch. And from film footage, she seems to have had a rather formal relationship with him. Andrew came along when she'd been Queen for nearly 10 years, was more relaxed in her role, and had more time to spend with him. He's allegedly her favourite too, plus he seems to have fitted in better at school and was the best looking out of the Queens children.