Cannes 2016
Julia Roberts turned 50 on 28 October AFP/Getty

Julia Roberts has revealed the three key reasons for her happiness. According to the Pretty Woman star, the reasons are marriage to "the right person, give birth to a redhead, and have great girlfriends".

The Notting Hill star has been married to Daniel Moder since 2002, and they share three children - twins Hazel Patricia and Phinnaeus "Finn" Walter, 12, and Henry Daniel, 10. The "redhead" that Roberts is talking about is her son Finn.

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Roberts also opened up about motherhood while posing for the cover of the December issue of InStyle magazine.

Speaking about her brood, Roberts said: "The thing is we have these three human beings who are just a complete reflection of the affection we have for each other."

Roberts' twins Finn and Hazel are turning 13 on November 28 and seeing her children grow up is a bittersweet experience for her.

"The cliches are true. I'm so proud of them but also... I tried to carry somebody up to bed the other night, and it was just ...All right, you're gonna have to get on your feet and sleepwalk because I just can't get up the stairs," Roberts said.

Roberts also revealed her plans for Thanksgiving, saying that she will be busy cooking in the kitchen.

"I truly love cooking. One of my favourite things about Thanksgiving is you can just spend days cooking," she said.

She continued. "You aren't obligated to do anything else. I think I got that from [my mother] and learned by being in the kitchen with her, watching her do it." Roberts' mother Betty died of lung cancer in 2015.

Roberts, who could easily give any 20-year-old a run for their money, also talked about what it means to be a 50-year-old. She said there was "nothing different about this birthday than any other one."