It is a little strange to think of the actor as 'Grandpa Charlie,' - even to Sheen himself, who shared the news with David Letterman.
'Me as a grandfather, Dave... I don't know. It's like the world's going to crack in half,' he joked.
But Sheen quickly added: 'It's fabulous. It's just not a title I'm ready to adopt.'
Sheen, who became a father at 19 when his high school girlfriend Paula Profit gave birth to Cassandra, is also dad to daughters Sam, eight, and Lola, seven, with his second wife Denise Richards, and three-year-old twins, Bob and Max, with third wife Brooke Mueller.