I am skeptical of people who make such statements. If he deeply regrets it, what exactly would he expect his children would do to improve his life? It's not the children's job to save the parents from their emotional loneliness and give their life meaning. Children grow up and are their own people. If he deeply regrets how his life turned out, he would probably be unhappy even if he had children, or worse inappropriately demanding, placing his needs on the children.