The Duke of Sussex dropped the revelation in an interview with legendary conservationist Dr Jane Goodall.
He sat down with the scientist for a candid interview in the September issue of British Vogue magazine.
The issue was edited by his wife Meghan, with the pair meeting Dr Goodall with baby son Archie at their Frogmore Cottage home recently.
Harry and Dr Goodall discussed racism during their chat, as well as the environmental crisis and climate change.
But the Duke’s hopes of having a second child unusually popped up as the pair talked about the damage being done to the natural world.
Goodall had said: “It’s crazy to think we can have unlimited economic development on a planet with finite natural resources.
“There’s a lot of violence and war and suffering around the world today, but we’re part of the natural world, and if we can’t learn to live in harmony with it, then this is going to get worse.
“There will be more conflicts, people fighting over the last fertile land, the last fresh water.”
Harry replied to Dr Goodall: “What we need to remind everybody is: these are things that are happening now.
“We are already living in it. We are the frog in the water and it’s already been brought to the boil. Which is terrifying.”
Dr Goodall responded: “Happening and happened,” before adding: “It is terrifying. Especially as you’ve just had a baby.”
“I know,” Harry said. “It does make it different. I think, weirdly, because of the people that I’ve met and the places that I’ve been fortunate enough to go to, I’ve always had a connection and a love for nature. I view it differently now, without question.
“But I’ve always wanted to try and ensure that, even before having a child and hoping to have children.”
The conservationist then laughed as she said: “Not too many!,” before Harry replied: “Two, maximum!”
He added: “But I’ve always thought: this place is borrowed.
“And, surely, being as intelligent as we all are, or as evolved as we all are supposed to be, we should be able to leave something better behind for the next generation.”