Prince Harry gives insight into the royal "Fab Four" dynamic in public appearance together.

“We are stuck together for the rest of our lives,” is the happy but also daunting reality facing the royal family’s most endearing foursome.

Prince Harry was the one to admit such a relatable truth, speaking at the Royal Foundation Forum on Wednesday – a new, annual event to showcase the royals’ charity work.

He was sitting on stage alongside his new fiancée, former actress Meghan Markle, his brother, Prince William, and, of course, Catherine, Duchess of Cambridge, in a public appearance together.

Watch Prince Harry discuss his family in the video below.

“We have different opinions and they work really well together,” Prince Harry, 33, continued, News Corp reports.

“Working as a family does have its challenges; of course it does. The fact that everybody is laughing shows they know exactly what’s it like.”

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And laughing they were. The banter between the four – who have been giving he nickname the “Fab Four” – was everything us mere mortals were imaging it should be.

“We have four different personalities and we all have that same passion to make a difference,” Prince Harry told the audience.

But “oh yes!” they have disagreements, he laughed. “They come thick and fast” .

Kate, 36, and Meghan, 36, looked like natural sisters-to-be wearing similar shades of blue.

(For those wondering, the Duchess is reportedly wearing a dress from maternity brand Seraphine and her soon-to-be-sister-in-law is wearing a sleeveless trench dress from Jason Wu with Aquazzura heels.)

Prince William, 35, said he was “delighted” to be at their “first Royal Foundation event with Meghan”.

Meghan 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, according to AAP.

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

And just like that, the Fab Four of the royal family is complete.