Oliver James Montgomery-Katharine McPhee Shares Rocking Video of 3-Year-Old Son Rennie Drumming Onstage

Katharine McPhee's son is Oliver James Montgomerydrumming up to the next level. 

After all, 3-year-old Rennie—whom the Smash alum shares with husband David Foster—just made his onstage debut during the couple's An Intimate Evening with David Foster and Katharine McPhee tour in Washington D.C Feb. 25. 

"Had a VERY special guest join us on stage for the first time," Katharine wrote in a Feb. 26 Instagram post. "#ProudMom."

And while Rennie has some prodigy-level musical talent, which his parents have shown off before, he wasn't technically performing during his parents' show. 

"I hope people realize that JR—the legendary @johnjrrobinson1—our incredible drummer is drumming," Katharine added in a comment under her post. "Rennie is only copying to the best of his ability unmic'd—and it was cute to watch his first on stage debut."

It seems only fair that Rennie would be so talented given his parents' backgrounds. Katharine, for her part, made a name for herself after scoring runner-up on season five of American Idol and went on to release five studio albums in tandem with a robust acting career. 

Meanwhile, composer and producer David flourishes on the more technical side of the industry. The 74-year-old—also father to children Alison Jones, 53, Amy S. Foster, 50, with ex-wife B.J. Cook, as well as Sarah Foster, 43, Erin Foster, 41, Jordan Foster, 38, from his marriage to Rebecca Dyer—has earned 16 Grammys throughout his decadeslong career. 

As for how David feels toward his son's budding musical flair? 

"You would think between Kat and I, we probably would have a child that would be musical." he told E! News last year. "I hope that he at least finds joy in music."

It seems safe to say that this musical duo has passed on their joy for sound down to their son. Read on for a look back on David and Katharine's best moments. 

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."