Charlie Sheen -- Sure, I'll Have Kids With My Fiancee

Charlie Sheen -- who is paying $110,000 a month in child support for his 4 minor children, may have been twice bitten but he's game to have more kids with his new fiancee.

Sheen tells TMZ ... he's absolutely open to having children with Brett Rossi. At 24 she's not experienced the joy of childbirth, and she wants a family. Charlie will accommodate her, but he says not right away. As Charlie put it, "I'm having way too much fun with her right now. So much fun it should be illegal."

Charlie says Brett has spent time with twins Bob and Max. He says she loves them and vice versa.

Charlie -- who's been married 3 times -- also tells us he WON'T demand a formal prenup from Brett. Charlie says, "Prenups poison marriages." According to Charlie, his form of prenup will be short and sweet ... one line: "You keep your s**t and I'll keep mine."