AceShowbiz - David Foster is hopeful that the 34-year age gap between himself and Katharine McPhee is starting to seem less "weird." The 74-year-old producer knew the age difference in his fifth marriage is "obviously not the norm" but he thinks now they have been together for several years, they are starting to look "right" together.

"Well, it's certainly not the norm. And I get it," David told the Daily Telegraph newspaper while referencing the 26-year age gap between his friend Celine Dion and her late husband Rene Angelil.

"But what I hope is happening to us is, when Celine and Rene first got together, I started working with her when she was 19. Then when I found out that they were together, and she was maybe 20, and he was 45 or whatever the age gap - not quite as big an age-gap as us - it seemed weird for sure."

"But then, magically, being around them after year three, year four, year five and on into a decade, it just looks right. And I'm hoping that we just look right now. Because it's been six years. It's obviously not the norm. But it really works for us."

However, David - who has five adult daughters from his previous marriages and two-year-old son Rennie with Katharine - admitted he is "so happy" his wife turns 40 in March. He laughed, "I'm so happy that she's turning 40 in a couple of months, because then at least [I can say] 'My wife's in her forties!' "

The veteran producer acknowledged age gaps can be a factor in relationship problems, but insisted all marriages are "challenging" in some way. He said, "There's so many things that can bring a marriage down. Money, infidelity, children, stepchildren. Age-difference is one of them. But it's only one."

"So if you have all the other stuff together, and you're not fighting about all that other stuff, then, yeah... I mean, it's challenging in some areas for both of us. But marriage is challenging, period."