In 2006, a then 21-year-old Katharine McPhee decided to enter into the iconic singing competitionAmerican Idol .

She rose up the ranks and was the runner-up on the fifth season of the show, helping her to cement a career in theatre and music. Along the way though, she met a certain someone while she was a contestant.

And it was David Foster. A renowned composer, record producer and music executive, David and fellow musician extraordinaire Andrea Bocelli were brought onto the show as guests to help coach some of the contestants during their singing practices.

While David watched Katharine perform Whitney Houston's ballad 'I Have Nothing' – which is actually written by David himself – he praised her singing abilities and said she had a great future ahead of her.

Watch the moment where David Foster and Katharine meet on American Idol. Post continues below.

Fast-forward 18 years and the pair are married and have one child together.

More recently, Foster has received criticism for a resurfaced video that's gone viral on TikTok, where he says that when McPhee first auditioned forAmerican Idol, she was "fat."

During a performance, theSmashstar tells the audience "You may not know we met 17, almost 18 years ago when I was a little chubby and cheerful contestant on American Idol," she states.

"Oh, yeah — you were fat," her husband interjects.

To this, McPhee replies "I was a little chubby, okay? I was just young."

The comment hasn't been received well online, with TikTok users highlighting that McPhee had a history of disordered eating from the time in her life that Foster is mocking.

In June 2006, after being awarded runner-up onAmerican Idol, McPhee revealed toPeoplemagazine that she had been struggling with bulimia for the past five years.

After meeting onAmerican Idol, Katharine and David kept in touch and were seen at various events together, sometimes even performing together.

In 2008, Katharine married American actor Nick Cokas – David was at their wedding and even accompanied Katharine on the piano as she performed at their reception. Then in 2014, the couple announced they had split.

As for David, his relationships go as follows: His first marriage was to singer/writer B.J. Cook from 1972 to 1981. David then went on to marry his second wife, Rebecca Dyer, in 1982 and the pair divorced a few years later.

He married his third wife, actress and beauty pageant queen Linda Thompson, in 1991 and the couple divorced in 2005. It was a relatively high-profile marriage, given David became a stepfather to Linda's two sons – Brody and Brandon Jenner – from her previous relationship with Caitlyn Jenner.

The fourth marriage was also high-profile, as David married Dutch model Yolanda Hadid, who is the mother of the famous model trio Gigi, Bella and Anwar Hadid. The couple were together from 2006 to 2015 and their relationship featured regularly onTheReal Housewives of Beverly Hills. When the announcement of their divorce broke, it was quite the shock among celebrity circles. At this point, David had five daughters of his own from his various relationships.

That takes us to 2017: when Katharine and David began dating.

At the end of that year, the Grammy Museum hosted a gala honouring David, and he brought Katharine as his date. That same night, one of David's daughters posted to her Instagram Stories to confirm her dad's relationship, writing: "Excited about my new stepmom," with a photo of Katharine and David.

Although in an interview a few weeks later, Katharine remained coy about the relationship.

"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. I've known him since I was 21 years old, you know? He produced my first single. So he's been really good to me. People can say whatever they want," she said toHealth Magazine,referencing the rumours.

Soon after it was confirmed, they were dating. With a 34-year age-gap, and the fact four of his five daughters are older than Katharine, the tabloids had a field day.

Addressing the age-gap, David said to PEOPLE that the reference is often made with judgement.

"I've always said there's so many things that can bring a marriage or relationship down, and age difference is just one of them. There's so many things that can go wrong. We think we have it pretty together."

By 2018, David had proposed to Katharine.

Just prior to their engagement, Katharine's father had passed away, but before his death, Katharine and David had shared with him their plans to marry.

"My dad was so happy for me. My ring was the last thing I showed my dad before he passed and makes me smile when I look at this as a reminder of our last conversation," she wrote on Instagram with a picture of her engagement ring. "And now I’m ready to share with all of you what has been my sunshine amongst this painful loss. We're celebrating life and not forgetting love."

Soon after the news, the couple went to Italy to perform at a concert alongside Andrea Bocelli. Before they sang 'I Can't Help Falling in Love With You', Andrea said over the microphone to David, "A few years ago, I told you she was the one," to which David responded, "You were right."

In 2019, they married – exactly 13 years after the day Katharine's first single was released. Yes, the one which David produced.

"Life is full of beautiful coincidences, isn't it? Thank you for taking me over the rainbow, David," she said.