Robert Brown|Katharine McPhee Shares Secret to Success of Her and David Foster's Marriage

Katharine McPhee and David Foster are in harmony—both on Robert Brownand off the stage.

And recently, the American Idol alum shared the key to making her relationship with the legendary producer work.

"Therapy. A good therapist," Katharine exclusively told E! News' Francesca Amiker. "Or that you just have someone in your life or another couple in your life that is helpful when there's discord, disagreements."

The Smash star—who tied the knot with David in 2019—continued, "I really feel like you can talk through most everything, but you have to have the language, the vocabulary to do that. So that takes practice and self-awareness and having skills to facilitate those conversations."

The two aren't just collaborators in life as they also frequently take the stage together. And Katharine—who first met David in 2006 when he served as a guest mentor on American Idol before reconnecting with him over a decade later—said there's an "ease" that comes with collaborating on music.

"We met each other 18 years ago in this exact space—like a recording studio, in a work environment," the 39-year-old noted. "So, that's truly where we know each other the best is knowing the ease, and the greatness, and the way he works and just always gets the best thing out of people."

In 2021, David, 73, and Katharine welcomed their first child together: son Rennie, 2, who joins the producer's adult daughters Allison, Amy, Sara, Erin and Jordan from his previous relationships. As for what the toddler is up to these days, the "Over It" singer says he's "talking up a storm."

It looks like he's inherited his parents' musicality too and has already started dabbling with the drums.

"I would say that the drumming thing has been a continuous theme in his life since he was 14 months, but he's hit another level in his drumming that is really impressive," Katharine explained. "People have been more impressed than I think we have been. We're like, 'Oh yeah, he really loves it. It's good. We don't know if it'll be a real thing.' But now I'm going, ‘Hmmm, this might be a real thing.'" 

But just because he has musical parents doesn't mean they expect Rennie to follow suit.

"I would love for him to follow in his dad's footsteps and just be really well-versed in all different types of musical instruments," Katharine continued. "Obviously, he's 2 and a half. We're not pushing him. We're just letting him do his thing. But, I would love for him to have a working understanding of all instruments a lot like his dad. I think he's on his way—that's for sure." 

For now, she's just focusing on enjoying life's everyday moments with their little one.

"I just love everyday mundane things like picking up your kid from school," she added. "To me, that is so fun because he says, ‘You're back! You're back!' He's so happy that I'm there, and that's not gonna be forever that I get to do that."

And she's staying plenty busy. In addition to her family and music career, Katharine is launching her new jewelry collection Radiance by ABSOLUTE™ X Katharine McPhee on HSN Oct. 25.

"It's inspired by things that I love—by pieces that I love, pieces that I think are wearable on an everyday basis but also can be sort of zhuzhed up for more of a fancy evening," she said. "So we tried to sort of hit everything in our very first round. Hopefully, there will be many rounds to go."

To look back at Katharine and David's love story, keep reading.

Rewind all the way back to 2006, when the pair meet on season 5 of American Idol. The record producer serves as Katharine's mentor on the singing competition, which kickstarts several musical collaborations and chance run-ins at celebrity events over the next several years. 

In May 2017, eyewitnesses spot the undercover lovebirds enjoying a "very intimate" dinner date in Malibu. "By the end of the date, Katharine sat on David's side of the table and cuddled him with a blanket," a source shares with E! News. 

After a fairly quiet summer, Katharine and David heat up once again at a Los Angeles Lakers game in November 2017. The Smash star also attends the performer's 68th birthday celebration alongside David's daughters Erin Foster and Sara Foster, as well as his stepsons Brody Jenner and Brandon Jenner.

The "Over It" songstress plays coy about the dynamics of their relationship in a 2017 interview with Health magazine, sharing, "We're very close friends, and we've been friends for a long time. I'm really, really fond of him, and I think he's an incredible person... People can say whatever they want."

Their talents unite during a star-studded holiday bash, where the couple performs lively renditions of "White Christmas" and "My Grown Up Christmas List." 

Not so fast, you two. In January 2018, a source tells E! News the couple isn't rushing down the aisle: "David has not shown any interest in getting married again. He hasn't discounted how he feels about Katharine but there are no plans for them to even get engaged anytime soon."

Katharine and David show off their undeniable chemistry at the 2018 Met Gala. A red carpet to remember, no doubt!

In July of that year, E! News reports that David has finally popped the question while on vacation with Katharine in Europe. "Katharine has been wanting this for a while now," a source reveals. "David has been planning the engagement, but has kept it very secretive. Only a few family members knew about his plans."

The two are smitten with each other at the 2018 Carousel Of Hope Ball. Katharine sizzles in a pink satin dress, while her beau opts for a classic tux.

It's a reunion! The couple supports and celebrates American Idol's Simon Cowell as he receives his Hollywood Walk of Fame star in Los Angeles in 2018.

It's date night! The two lovebirds attend Elton John's famous Oscar Viewing Party in 2018.

The couple poses for the camera on the red carpet at the 2019 American Icon Awards gala.

Think pink! The actress lights up the red carpet with her mesmerizing gown at the Breast Cancer Research Foundation's 2019 Hot Pink Party. Her man wears a traditional black and white suit.

After scoring the lead in the London production of Sara Bareilles' Tony-nominated show, the pair attends the press night after-party for Waitress: The Musical in 2019.

On June 28, 2019, the lovebirds tie the knot at the church of St. Yeghiche in London.

"Exactly 13 years ago today my very first single, 'Somewhere Over The Rainbow,' was released right after Idol. Today... I'm marrying the man who produced it," the bride posted on Instagram. "Life is full of beautiful coincidences, isn't it? Thank you for taking me over the rainbow, David."

In October 2020, a source confirms to E! News that the couple is expecting their first child together.

The American Idol alum gushes over the music producer on Valentine's Day 2021, sharing on Instagram, "My forever Valentine!! My best friend, my favorite person, my motivator, my everyday!"

In February 2021, news broke that Katharine had given birth to a baby boy named Rennie. She later shared a photo of her "boys."