This morning Kemper asked me what "sex" means. I explained that it means a couple of things. The first is that whenever you have to fill out a form for school, camp, etc., it asks you what your sex is and that they want to know if you're a boy or a girl.
Then I said that it also is something that two people do together when they really love each other. He thought about this and replied, "So when people love each other, they say 'sex' to each other?" Um, not quite. But that was the end of the discussion so perhaps he got what he needed for now.