The way James Middleton introduced his wife Alizee Thevenet to Kate Middleton wasn't quite a storybook moment.

The Princess of Wales' younger brother shared how his then-girlfriend accidentally met his older sister, Prince William and their children, Prince George, 11, Princess Charlotte, 9, and Prince Louis, 6, when the pair unexpectedly decided to stay at their parents' home in Berkshire after a wedding.

"We let ourselves in and tiptoe around in the dark, not wanting to wake anyone," James recalled in his novel Meet Ella: The Dog Who Saved My Life, per an excerpt published by Daily Mail Sept. 15, "then catch a few hours' sleep before I'm woken at 7.30am by giggling at the ­bedroom door."

Surprise! It was George and Charlotte.

"I hadn't ­realised all three children are staying for the weekend with my sister and William," he wrote. "Alizee is still sound asleep, so I gently shush the children and we go downstairs where Catherine and William are drinking their early morning tea in the kitchen."

As James got ready to take a cup to Alizee in bed, she wandered downstairs in his T-shirt. He was in awe of her calmness during the surprise run-in despite this being their first meeting.

"She just greets everyone warmly as if it's not remotely unusual to be meeting her boyfriend's sister and brother-in-law for the first time wearing only an oversized man's shirt," he explained. "'Hello,' she says, proffering her hand and with no awkwardness at all we're soon all chatting and the children are asking all kinds of cheeky questions at 100 miles per hour."

The kids couldn't help but pry for more details from their uncle. "I tell Charlotte and George, yes, she is my girlfriend and introduce her to them," he added, "then we are all talking and laughing as if she has been part of the family for years."

That same day, their parents Carole Middleton and Michael Middleton came home. As they all began to part ways the next day, Kate shared some sweet words with James.

"I get a special squeeze from Catherine, who whispers in my ear, 'She's just great,'" he wrote. "Mum's warm smile tells me she agrees. All my stars have aligned: Alizee is perfect for me and my family adores her. 

James and Alizee eventually tied the knot in 2021 and welcomed their first baby last October. 

The excerpt was published just days after the couple celebrated their wedding anniversary. "Je t’aime, mon coeur," he wrote on Instragram Sept. 11 "Happy anniversary Alizee. Our third as husband & wife, our second without Ella but our first as parents."

For the latest breaking news updates, click here to download the E! News App