Harry, 25, whom William describes as a "free spirit," recognizes his key role will be by his brother's side.
"I will always give him as much support as I can," Harry says in a new interview, William and Harry – the Brother Princes: Tonight, which airs Thursday in the U.K. on ITV1. "Sometimes it's probably not valued, which is understandable as the older brother always thinks they know best. But I always give him my opinion where it's needed."
Harry adds, in the special documentary made during their trip to Africa, "When I think he's wrong I'll tell him he's wrong. Nine times out of 10 he puts that in his back pocket and carries on anyway, but in later life who knows?"
Brotherly AppreciationWilliam, 28, reveals in the film that he appreciates his younger brother. "We get on very well, we have a lot of banter. We both keep each other grounded," he says. "Both of us agree that you've got to be grounded and understand things from the bottom up."
And he adds, "I think Harry's got a very free spirit and a very intuitive way of dealing with things, looking at problems. He very much throws himself into it wholeheartedly. He's got a big heart and he wants to make a difference. I've seen it with [his charity], Sentebale. Out here, he is the star."
They also speak about their late mom, Princess Diana, who inspired their charitable work, which was highlighted in the six-day tour through three African countries. Harry finds himself pondering what she'd be doing as they began working to help others.
"Whatever we do, wherever we are and whoever we're with I particularly always wonder what she'd think, what she'd be doing if she was with us now," he says, "if she'd be sitting here having a laugh, whether she'd be in the background sticking her tongue out or whether she'd be playing football with the children."
Thinking of her "keeps us going every day," he says.