That connection was on full display during Celebrity Fight Night in Italy on Sunday, where McPhee performed “I Can’t Help Falling In Love with You” with Andrea Bocelli and barely took her eyes off of Foster, who accompanied on piano.
“A few years ago I told you she was the one,” Bocelli told Foster just before the duet, to which he responded, “You were right.”
The luxurious weekend-long charity event, which raises funds for the Barrow Neurological Institute and the Muhammad Ali Parkinson Center, nearly doubled as an engagement celebration for the pair. After dodging relationship rumors for months, they confirmed in July that Foster had proposed with a sparkling emerald-cut diamond ring while they vacationed in Anacapri, Italy.
Opening up for the first time in this week’s issue, the hit-making musician, 68, and former Smash star, 34, tell PEOPLE that despite their 34-year age difference (which has spurred a number of lighthearted jokes between McPhee and his daughters Sara, 37, and Erin, 35) they’re much more focused on all that they have in common.
“She didn’t catch my eye on the first day because I was so busy trying to do my job,” says Foster, who went on to produce McPhee’s first single. “But,” he adds, “the reality is that in the last 12 years I’ve always had a connection with her.”
What began “on a friend basis” says McPhee, later transformed into a romance that took them both by surprise. “There are just a lot of things when you look at the history of our relationship, neither of us could have written it. I would never have imagined that this would be our future together.”
As for what bonds them, “the fact that we are both in the music industry helps,” says Foster, who recently embarked on his The Hitman Tour. McPhee recently wrapped her run in Broadway’s Waitress. “We understand each other,” he says.
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And while they know their significant age gap has been a hot topic, they’re tuning out the noise. “It doesn’t make sense to a lot of people, but it does to us,” McPhee says of their love.
“He has things to learn from me and I have a lot of things to learn from him,” says McPhee, “so I think we have a nice yin and yang.”
For more on David Foster and Katharine McPhee’s Romance, pick up this week’s issue of PEOPLE, on newsstands Friday.