New Twist On The Birds And The Bees

I'm dreading the time that my son asks me about the birds and the bees. I mean, he's still too young to be concerned about that. But he has mentioned that he knows what sex is and he even explained what being gay is. He's got a good source of information at school it appears. But he threw a question at me last night that I wasn't prepared for.
"Dad, how do you stop having babies when you are married?"
Well, I didn't wish to explain contraception or even say that you stop having sex therefore I replied with "Stop kissing." He accepted that. I think that it was a reasonable answer at this stage in life. There is some truth to that statement, isn't there?