The `Forget You` hitmaker has revealed his stepdaughter Sierra - whose mother is the musician`s first wife Christina Johnson - has given birth to a baby boy.
During an appearance on Chelsea Handler`s talk show, he said: "I`m a grandfather. I`m 35. She had a son so I have a grandson."
The singer`s stepdaughter appeared in an episode of MTV reality show `My Super Sweet 16` - which focuses on the birthday parties of wealthy teenagers.
Cee Lo admits she was actually 15 when her `coming of age` bash was shown but MTV wanted to televise the celebrations anyway.
He said: "She was actually turning 15 on that show. MTV took a liking to her and they allowed her to be an exception for this show."
When Chelsea reminded him Sierra had flown to the party via helicopter and asked if she thought it was a bit extravagant, the Gnarls Barkley star replied: "It`s all for the sake of entertainment. It`s just good, clean fun."