The 'What Happens in Vegas' star - who, at 30, is 15 years younger than the Hollywood beauty - says marrying Demi and becoming a stepfather to her three daughters has made him happier than he could ever have imagined.

He said: "Demi has made me complete. And the girls are the icing on the cake that is my life. The love they give me is open and unconditional and everything I do revolves around making them as happy as they have made me."

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Ashton also revealed he has no problem with the age gap between him and 45-year-old Demi because he is used to being around older people.

He told a British newspaper: "My whole life, I've always been around older people. My friends were always a little bit older and when I was young, I spent a lot of time with my mom and her friends.

"I mean, I feel so darn grown up now I'm 30, even though the number is inconsequential. It should be all about where you are in life and how much responsibility you've taken on, not how old you are. For me, turning 30 was just an excuse to throw a party."