Charlie Sheen
Charlie Sheen told David Letterman Monday that he's nervous about becoming a grandfather. Reuters/Mario Anzuoni

Charlie Sheen has many titles -- actor, bad boy, “winning” -- but the “Anger Management” star admits that there’s one he’s not quite ready for, grandpa.

Sheen’s 28-year-old daughter, Cassandra Estevez, will give birth to her first child later this year, and the 47-year-old actor told David Letterman he is excited for his grandchild, but is also a bit nervous, according to Us Weekly.

Sheen appeared on the “Late Show With David Letterman” Monday and dished about the new addition to his family.

"Me as a grandfather, Dave ... I don't know. It's like the world's going to crack in half," Sheen told Letterman. "It's fabulous. It's just not a title I'm ready to adopt."

Estevez is Sheen’s oldest daughter, whom he had with his high school girlfriend Paula Profit when he was 19, according to the Daily Mail.

Sheen gave Estevez away when she married her high school boyfriend Casey Huffman in 2010.

The actor may not be used to the idea of being a grandfather, but has certainly become accustomed to the role of dad.

In addition to Cassandra, Sheen has two daughters with second wife Denise Richards, Sam, 8, and Lola, 7, as well as 3-year-old twins, Bob and Max, with third wife Brooke Mueller.

Sheen told Letterman there is one perk to being a grandfather to which he is looking forward.

"Well, yeah, because you can leave the kid!" he said.