His son, William, said that he would like Charles to spend more time with his grandchildren.
The documentary also sees Camilla, the Duchess of Cornwall, say that her husband is fantastic with children, mentioning her own four grandchildren from her previous marriage.
"I asked him [Charles] to and I think he knew it was coming and he immediately said, 'Yes, of course, I'll do whatever Meghan needs and I'm here to support you, '" Harry said, according to People.
He said in developing his role in the early days, he took advice from politicians including Conservative prime minster Sir Alec Douglas-Home when foreign secretary, and Labour prime minister Harold Wilson.
Are you a fan of Prince Charles? "Err, no! Though that is what I wanted to say but I was very grateful for him to be able to do that".
"Because as most families would do, you are anxious about having them around and making sure their health's okay. And then William was longing to meet her and so was Catherine, so you know being our neighbors, we managed to get that in a couple of - well, quite a few times now, and Catherine has been absolutely..."
One source tells ET that 'Meghan and Harry, who want to use their platform and their profile to further their humanitarian and their charitable interests, really want to pass those same values on to their children.
"It's a flawless time to consolidate a little bit", William said, "as most families would do, you are anxious about having them around and making sure their health's OK".
"This is a man who has dinner ridiculously late at night and will fall asleep on his notes". "When we were kids, there were bags and bags and bags of work that the office just sent to him".
"I think it's vital to remember there's only room for one sovereign at a time, not two, " he said in the one-hour programme ahead of his 70th birthday November 14.
Prince Harry and Meghan Markle faced a lot of drama leading up to the royal wedding on May 19, but Prince Charles barely needed asking before stepping in to save the day, the Duke of Sussex revealed in a new interview.
As he walked through a local market in the capital Port Vila, he asked: "Am I allowed to buy one or two things?" first pointing to a handbag for his wife Camilla.