Prince William and Kate Middleton 'Fuming' Meghan Markle's Kids Call Bestie Serena Williams Their 'Aunt,' As Shock New Video From Sussex Family Reopens Old Wounds — 'Their Kids Have No Idea Who Their Cousins Are!'

Meghan Markle has referred to her pal Serena Williams as an "aunt" to her young kids Archie, 5, and Lilibet, 3, – which has infuriated their IRL aunt Kate Middleton, RadarOnline.com can report.

Sisters-in-law Meghan and Kate have had an icy relationship, and referring to the tennis star as family has reopened old wounds between the two.

Markle, who is busy promoting her new Netflix show, With Love, Meghan, shared a very rare video of Williams, 43, playing Candyland with Lilibet.

The Duchess of Sussex is notoriously protective of her kids, and even when she does tease a look at them, it's usually the back of their heads or some other undistinguishable angle.

In the short video, which she shared to her Instagram stories, Lilibet was seen from the back dancing around in a cute pink top with floral pants. Smiling next to her was Wimbledon champ Williams clapping with glee.

Markle, 43, captioned the video: "When the aunties come to celebrate…and to play. Love you, Serena Williams."

Insiders say giving Williams a family title has hurt Archie and Lilibet's actual aunt Middleton, 43, and Prince of Whales uncle William, 42. But the Duke and Duchess of Sussex have had a rocky relationship with their royal side for years now.

A source told New Idea: "It's so sad that Meghan and Harry's children don't have any relationship with their real aunt and uncle. In fact, that applies to their whole extended family on Harry's side."

After Harry and Markle ditched palace duties in 2020 to head to Hollywood, the Suits star, who comes from mixed-race parents, suggested that some of her in-laws were racists for questioning the skin color of the couple's unborn son, while Harry called his father, King Charles, cold and unfeeling, and accused his stepmother, Queen Camilla, of backstabbing him to make herself look better.

However, our insiders say Duchess Meghan's post-palace life has fallen short of her expectations: "Her and Harry's $20million Spotify podcast deal went bust, her new Netflix show has been trashed by critics, and her fledgling lifestyle brand – now known as As Ever – has stumbled out of the gate."

That has led the ostracized pair to try to thaw the chill lately, and renew connections with their family. But Markle's post has been received as a setback.

Another source told Women's Day: "Meghan's video is another reminder for Kate that she'll never play a part in Lili's life. It's an extraordinary situation – some suspect she is banned from seeing her own niece and darling nephew."