Entertainment Music David Foster's Daughters Joke Their Only Issue with His Wife Katharine McPhee 'Is How Hot She Is' David Foster opens up about how he found his happily ever after with wife Katharine McPhee in this week's issue of PEOPLE By Brianne Tracy Brianne Tracy Instagram Twitter Brianne Tracy is a staff writer on the PEOPLE music team. She has been with the brand since starting as an intern nearly six years ago, covering all things entertainment across print and digital platforms. She earned her Bachelors in Broadcast Journalism at the University of Southern California and has been seen on Good Morning America. People Editorial Guidelines Published on July 1, 2020 02:30 PM Share Tweet Pin Email Though much has been made of David Foster and wife Katharine McPhee's 34-year age difference, the hit record producer's daughters Sara, Erin and Jordan have no problem with their relationship — minus one thing. "Our biggest issue with [Katharine] is how hot she is," Erin, 37, tells PEOPLE in this week's issue, on newsstands Friday. "Her body is insane. When she comes over for family Sundays, I'm like, 'Do not get in a bikini.' My husband's always like, 'Kat, get in the pool!' And I'm like, 'Simon...'" During their family Sundays, a new tradition that started up when the coronavirus lockdown began, Sara, 39, says all of their husbands "hang on the side ogling her." "Even my 2-year-old son [Otto]," Jordan, 34, adds. Erin, David, Jordan and Sara Foster. Anais & Dax The three women say McPhee — whom David met in 2006 when he served as a mentor to her and other contestants on season 5 of American Idol and married on June 28, 2019 — has only been a positive addition to their lives. "Interestingly, the age difference has played a role in a positive way," Erin explains. "Our dad comes from a generation where women are more passive. He is also passive about his feelings. Kat has really pushed him to open up. We could get into a fight, and then Kat's like, 'No, you have to pick up the phone, call your daughter back.' She's a facilitator, which is really important. She pushes him to be more emotional and more vulnerable." Katharine McPhee and David Foster Celebrate One-Year Wedding Anniversary: 'Here's to the Future!' Jordan points out that before McPhee, 36, David, 70, had "been with age-appropriate women forever." "Age-appropriate hasn't worked in the past," she says of her dad, who was married and divorced four times prior to marrying McPhee. "So I think this is fine." When it comes to his and McPhee's age difference, David realizes that "haters are always going to be haters." "But, the way I've resolved it, there's 10 things that can bring a marriage down," he says. "There's infidelity, there's geography, there's finances, there's kids ... There's so many things that can bring a marriage down. Only one of the 10 is an age difference. So if we feel like we have the other nine right, that we're really solid on the other nine, the one is not going to break us up." David Foster and Katharine McPhee. David Foster/Instagram David also gives McPhee a lot of credit for coming "into this," meaning his family of five daughters (in addition to Sara, Erin and Jordan, he has daughters Allison, 50, and Amy, 46, from previous relationships). "I think she navigates it really, really well," he says. "And so do they. Because they could be horrible. It sure makes it easier for me that they get along. It's not a fleeting thing, either. It's been a few years." RELATED VIDEO: Family Means Everything to the Fosters For David's daughter Amy, who is a songwriter based in Portland, Oregon, a memorable bonding moment with McPhee came last year. "A year ago I was diagnosed with breast cancer," she says. "When I had my mastectomy, my dad and Kat flew in for that and stayed with me. She's amazing. Kat is not a trophy wife — she has a lot to say, she's interesting, she has a fantastic career and she's nobody's trophy. You don't even think about the age difference when they're together because they both are emotionally the same age, which is either 36 or 70, I don't know. Sometimes my dad is super young and sometimes Kat is super old." Erin, Sara, David and Jordan Foster. Anais & Dax At the end of the day, David's daughters are just happy that he's happy. "We've been through a lot with each other, and we've arrived at a place in our lives where we're all happily in our own relationships," says Erin, who married her husband Simon Tikhman on New Year's Eve. "We want our dad to be happy in his relationship." "We are not dating our dad so we are not competitive with the woman who comes into his life," she adds. "We want him to be happy, and it doesn't matter if she's our age or if she's his age because we just want him to be with a good person. And the truth is, ironically, it's much easier for us to get along with someone who's our age because she's similar to us. She's someone who we would be friends with. Adds Sara: "She pushes him to be a better person, which is all we want." Recently, David, his daughters and McPhee came together for a new documentary, David Foster: Off the Record, which will be available to stream on Netflix Wednesday. In it, the 16-time-Grammy winner opens up about his life and career.