Rumer Willis used to have pictures of her step-dad Ashton Kutcher on her bedroom wall - until he started dating her mom Demi Moore.

Willis, whose father is Hollywood actor Bruce Willis, admits she used to have a crush on Kutcher and was shocked when she found out he was romancing her mother.

She tells British magazine Cosmopolitan, "It was strange when mom, who is 15 years older than Ashton, started seeing him (in 2003). I was 15 and he was a heart-throb to me - I had pictures of him on my wall!

"I remember mom saying her new 'friend' was going to hang out with us. I said, 'What's his name?' and she said, 'It's Ashton'.

"And I said, 'Whoa - Ashton Kutcher?' I freaked out a bit and blushed."

But Willis, 20, insists that she didn't feel awkward around the actor for long, because she could see he was so in love with Moore.

She adds, "I realised I'd never seen my mom happier. It was like watching two sixteen-year-olds going to the prom."

Kutcher and Moore married in 2005.