Sorry, admiral, it your fault. Parenting is not for the weak of heart. Fun to make but hard to raise.
In this email the "children" are all adults, with children of their own. Like many, by adolescence they probably became more susceptible to peer culture, societal influence, even educational malpractice, than parental guidance. They have been making their own decisions for years now, apparently choosing poorly despite parental efforts to provide guidance, yet expecting their parents to somehow "fix" things for them.
The father here should have set his limits and expressed his expectations years ago, and maybe the wayward "kids" would have woken up sooner. But then hindsight is always so easy, isn't it.