David Foster accompanied Katharine McPhee as she serenaded first husband Nick Cokas with Natalie Cole and Nat King Cole's hit "Unforgettable"

When Katharine McPhee walks down the aisle, it won’t be the first time David Foster sees her in a wedding dress.

The musician played piano at McPhee’s February 2008 nuptials to her first husband, Nick Cokas. Foster is seen sitting at the keys behind the bride in PEOPLE’s exclusive photos from the American Idol alum’s wedding.

He accompanied McPhee as she serenaded Cokas with Natalie Cole and Nat King Cole’s hit “Unforgettable,” after Cokas performed Billy Joel’s “She’s Got a Way.”

McPhee, 34, confirmed the engagement news herself (via Ariana Grande gif and text with Just Jared founder Jared Eng) on social media, writing that 68-year-old Foster popped the question during their vacation to Italy, which they’ve been documenting on Instagram over the past few days.

“He did it at the top of this mountain in Anacapri. Totally dark, only stars. Thankfully he didn’t push me off the cliff. He said it was one or the other. And in the end he spared me,” she joked via text.

Later on Tuesday, Foster also confirmed the happy news on social media, posting one of the many boat photos they have snapped of each other during their special vacation.

“🎼Yup!!,” he simply captioned the snap — though daughters Erin, 35, and Sara, 37, had more to say about their new (younger) stepmom. “Mommmyyyy,” Erin joked, while Sara wrote, “Out of the country. What did I miss?”

Back in September, as rumors of their romance popped up, Erin shared a photo of the two to her Instagram Stories alongside the captions, “Excited about my new step mom,” and “My parents.”

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At the time, a source close to David denied his romance with McPhee — and another insider explained that “Erin’s quite obviously tongue-in-cheek and sarcastic Instagram comments were pointed at those who can’t seem to grasp that her dad and Kat can be colleagues, collaborators and longtime friends without it being some big romance.”

“They can’t even perform together without people saying they’re headed down the aisle,” the source said. “Erin was messing with people who jump to conclusions.”

David and McPhee first sparked romance rumors in May 2017 when the two were spotted enjoying a PDA-filled dinner date at Nobu in Malibu. The pair was also said to have traveled together (with McPhee’s mom) not soon after on a Vancouver getaway.

The two have had a long friendship, with David first meeting the American Idol alum on the set of the hit reality singing competition when she was a contestant in 2006.

McPhee previously collaborated with the Grammy-winning producer for a few live performances, including his 2008 PBS tribute concert Hit Man: David Foster & Friends.

Despite many public displays of affection, the couple didn’t go public with their romance until they stepped out together at the 2018 Met Gala.

This will be the second marriage for McPhee and the fifth for Foster, who was most recently wed to Real Housewives of Beverly Hills star Yolanda Hadid.