Charlie Sheen is set to become a grandfather for the first time when his 28-year-old daughter, Cassandra Estevez, gives birth later this year.

The 47-year-old actor appeared on ‘The Late Show With David Letterman’ on Monday (14.01.13) and confirmed the happy news. He admitted to being nervous about the new addition to the Sheen family.

"Me as a grandfather, Dave… I don't know. It's like the world's going to crack in half,” he said.

"It's fabulous. It's just not a title I'm ready to adopt."

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When asked whether he’d be a good grandfather, he joked, "Well, yeah, because you can leave the kid!"

Cassandra is Charlie’s oldest daughter with his high school sweetheart Paula Speert. He also has two daughters, Sam, 8, and Lola, 7, with second wife Denise Richards, and twin sons Bob and Max, 3, with third wife Brooke Mueller.