By Breaking Celebrity News Staff

Someone pop open the champagne!

Ryan's Phillippe's ex-girlfriend, Alexis Knapp, gave birth to a baby girl last Friday, and the actor was by her side throughout.

There were reports that Phillippe would be demanding a paternity test once the baby was born, but US Weekly reports that there's no doubt in the actor's mind that he's the father.

"Ryan has known since the beginning that he's the dad. He is not taking a paternity test," the source says.

In an exclusive interview with Breaking Celebrity News, Alexis' mother, Marjorie Knapp confirmed that Ryan was the father of her daughter's then-unborn baby.

"Oh yes, I believe that it is his baby," Marjorie said. "I'm very proud of her. She did the right thing. She's keeping the baby and not having an abortion.

"She told me right away that it was Ryan's. They were in a relationship."

The Cruel Intentions actor began dating Alexis, 26, last June after he split from long-time girlfriend Abbie Cornish. But the beautiful couple parted ways in October when Phillippe was rumored to have been caught making out with another woman at his 36th birthday bash.