Having been tipped off by a good friend of mine who has a daughter Stone's age, I had the following conversation with my child recently:
mom: Stone, do you kiss your friends?
mom: Do you kiss them on their cheeks?
Stone: sometimes on the cheek, sometimes on the mouth.
mom: It's not good to kiss your friends on their mouths.
mom: Germs. You don't want to give others your germs or get their germs.
Stone: I have germs?
mom: Everyone has germs in their mouth. you just should keep those to yourself.
Stone: but I brush my teeth to get the germs out.
mom: I know you do and that's great. Let's just not kiss our friends on the mouth. Mommy and daddy kiss on the mouth because we're married.
Stone: what's married?
mom: It's when you pick a girl to be with forever.
Stone: Forever and ever?
mom: Yes. Forever and ever and ever. Daddy and I will be together forever. That's what it means to be married.
Stone: when do I get married?
mom: Well, first you have to go to first grade and then second grade and then third grade... all the way through grade 12. Then you have to go to college, and then after college you can pick a girl to be with forever.
Stone: mom, I don't think I want to be with a girl forever and ever and EVER!