Actor Ashton Kutcher turned 36 on Saturday, and the "Two and a Half Men" star celebrated his birthday with girlfriend Mila Kunis, who of course is his former co-star from "That '70s Show".

Over recent months, Kutcher seems more determined than ever to keep his private life private. Ever since his very public marriage to Hollywood actress Demi Moore ended in an even more scandalous divorce, he has seemingly wanted to keep his new relationship with Kunis more low key and out of the private eye as much as possible. This is something he admitted to in a recent interview.

"I am going to do everything in my power to have this relationship be private," said Kutcher to Elle Magazine in reference to his relationship with Kunis.

The couple's former high-profile relationships were all over entertainment news, and that has led to both of them wanting to keep things much more under the radar this time around.

Ashton Kutcher was formerly married to Demi Moore, where as Mila Kunis was formerly dating former Home Alone child star Macaulay Culkin for many years.

Kutcher and Kunis first met in the mid-90s on the set of That '70s Show. Kutcher was 20 at the time, and Kunis was only 15 when the show started. The "That 70's show" comedy series concentrated on the lives of a group of teenage friends growing up in the fictitious suburban town of Point Place, Wisconsin, from 1976-1979. The Fox show lasted 8 seasons from 1998-2006.

However, following Kutcher's split from Moore, the pair started dating, and they have been seen together at an array of family events recently. Last December, Kutcher attended the wedding of Kunis' brother with her. In addition, several weeks ago, Kunis went to Kutcher's twin brother Michael's wedding.

Kutcher's Two and A Half Men is currently in its 11th season. He replaced Charlie Sheen on the hit CBS series in Season 9 three years ago.