The royal couple appeared from their home in a video conference call with leaders within the Queen's Commonwealth Trust who are working to make positive use of digital media and take action against online bullying and the like.
The 35-year-old prince urged the activists to keep up the good work, and joked that he felt "way too old."
"You've got to stop, we're not old!" said Markle, 39, said in response.
"But it's true," Harry continued. "This is the world you're going to inherit."
In reference to their 1-year-old son, Markle added: "And Archie."
The Duke of Sussex agreed.
"It's on all of us collectively to make the world a better place, and we are," he said.
Also in the video, Harry mentioned his grandmother and her goals for the Commonwealth, which include young voices as the online scene continues to change.
"I think everything my grandmother wanted to achieve when she took this huge responsibility on, she’s managed," said the royal. "… Hearing you guys, and knowing the broad spectrum that QCT engulfs, you’re the definition of the 21st century Commonwealth, and what it means to be part of it. You are there, standing for equality, for mutual respect and for fairness."
Prince Harry, Duke of Sussex, Meghan, Duchess of Sussex and their baby son Archie Mountbatten-Windsor. (Photo by Toby Melville – Pool/Getty Images)
Markle then noted how the coronavirus pandemic has changed the way people are interacting with the internet, and the implications that can have.
"Everyone's mental and emotional well-being are perhaps more fragile than ever before, certainly with COVID and our dependability on devices right now in the absence of human interaction," said the Duchess. "People are going online more than ever before to feel community."
"When you look at what these platforms are capable of with that reach, and what that propels in terms of trolling," she added. "You can either train people to be cruel, or you can train people to be kind. It’s really that simple."
The couple are said to be hard at work in their new home state of California, as they're reportedly shopping a top-secret project around Hollywood.