Jack Osbourne to be a Dad!

Credit: Charles Eshelman/FilmMagic

Ozzy and Sharon are going to be grandparents!

Jack Osbourne and fiancee Lisa Stelly are expecting their first child, he announced Tuesday on Piers Morgan Tonight.

"I'm excited," Osbourne, 25, gushed on air. "I'm a little nervous." The Osbournes star-turned-director and actress Stelly confirmed their engagement just two weeks ago.

A friend of Stelly's told Us Jack is "a great influence on her," adding, "It's just no drama. More stable."

Jack is the youngest child of Ozzy and Sharon Osbourne; his baby-to-be will make aunts out of his older sisters Kelly, 26, and Aimee, 28.