David Foster thinks he ''won the lottery'' with Katharine Mcphee.

The 69-year-old musician - who got engaged to Katharine in July 2017 - can't wait to tie the knot with the 34-year-old actress soon.

Sharing a picture of his fiancé on Instagram, he captioned it: ''I won the lottery!!! (sic)''

The photograph was a repost of something Katherine had posted on her Instagram story, where she admitted she ''can't wait'' to marry David.

She wrote: ''Far away from each other but still can't wait to marry you @davidfoster (sic)''

And David's daughter Sara thinks Katherine will be a ''great addition'' to the family.

She said: ''She's great. She's a great addition. You know I've learned to not rule anything out [like David and Katherine having children]. I think anything is possible at this point. Who knows? ... She's wonderful. The other day she was like, 'I got you a facial,' and like that's so cool. My dad loves love and my dad loves commitment. My dad's always been married. He's never been single really. He's a real commitment, marriage kind of guy and I'm happy for him.''

And David's daughter Amy thinks he and Katharine are ''perfect for each other''.

She said: ''I know that some people have been hating on that relationship. All I can tell you is it absolutely works when you see them together. It's love. The haters [can] shut the f**k up because they are perfect for each other. I'm so close with [McPhee]. She's amazing and funny, fun, smart, elegant, timeless, beautiful, talented. I can't say enough about her.''