Meghan Markle has joined Prince William, the Duchess of Cambridge and her fiancé Prince Harry in their first ever official engagement together.

The royal power couples, dubbed the “Fab Four”, appeared on stage together on Wednesday to take part in the Royal Foundation Forum, with Harry joking the couples were “stuck together for the rest of our lives”.

The forum is a new annual event to showcase the projects run or launched by the royals’ main charitable and philanthropic vehicle which William and Harry set up in 2011.

“Catherine, Harry and I are delighted to be here this morning,” William, 35, told the London audience.

“And we are particularly happy to be at our first Royal Foundation event with Meghan. Today is a special day for us.”

Harry, 33, said he was “personally incredibly proud” of his soon-to-be wife, “who is equally passionate about seeing positive change in the world”.

Meghan, 36, will become the foundation’s fourth patron after she marries Harry at Windsor Castle on May 19. She has previously announced she is quitting her acting career and stepping down from her existing charitable work.

“We wait a couple of months and then we can hit the ground running but up until then I’m pretty excited,” she said.

“Harry and I see the world so similarly in our approach of being very hands-on with things.

“I have been fortunate enough to meet with some incredible women and organisations in the UK that are doing work here, but also knowing that some of the work I’ve done in the past has been in Commonwealth countries.”

The former Suits actress also spoke about the female empowerment movements #MeToo and #TimesUp, saying how she wants to use her profile to “shine a light on women”.

“”I hear a lot of people speaking about girls’ empowerment and women’s empowerment,” said Meghan.

“You will hear people saying they are helping women find their voices. I fundamentally disagree with that because women don’t need to find their voices, they need to be empowered to use it and people need to be urged to listen.

“Right now with so many campaigns like #MeToo and #TimesUp there’s no better time to continue to shine a light on women feeling empowered and people supporting them.”

The Royal Foundation focuses on issues such as helping young people, wildlife conservation, cyberbullying and supporting the military, most notably through the Invictus Games for wounded or disabled veterans, which Harry founded.

Last year, Prince Harry and Prince William were widely praised for leading a campaign to tackle the stigma of mental health illness and speaking out about how they had personally suffered following the death of their mother Princess Diana in a Paris car crash in 1997.

“We’re pretty tied up with planning a wedding at the moment but we’re really looking forward to working as a pair and as a four going forward and hoping to make as much of a difference where we can,” Harry said.

The four were pictured together leaving a service on Christmas Day on the Queen’s Sandringham estate but the event on Wednesday marked the first time the group had all attended an official event.

Asked if there were any disagreements with the family working closely together, William joked: “Oh, yes!”

Harry added: “They come so thick and fast. Working as family does have its challenges, of course it does. But we’re stuck together for the rest of our lives.”

“Togetherness at its finest,” Meghan responded.

-with AAP