I have a 5 year old and a 1 year old. Two boys. When I was pregnant with the baby, my oldest became pretty curious about how the baby would come out and of-course where it came from. I explained as much as I could to my then 3 year old in easy terms. He thought God put the baby in my belly, and [in his own thinking] was even convinced the baby would come out through my mouth. I remember teasing him on time and saying the baby would come out of my bellybutton and he looked at me like I was the dumbest person on the planet and said "No! You will go to the doctor and throw up the baby and the doctor will catch it!" Now, at 5, he's a little more sophisticated in his knowledge.
We've visited the Health Museum here and they had a display of the human body. You could walk through the brain and the ears, etc. They had a little movie for kids that showed how babies grow in the womb. So he now knows that babies come from eggs in the mother's belly.
So.......He's in the country at his Big Mama's house this week (my mother-in-law). One of my sister-in-laws drove the boys up there with her two older boys. When they got there, my son says to her,"Auntie O, you're my daddy's sister, so you're my auntie." She said yes. He said "K1 and K2 are your sons, so they are my cousins." She said yes. Then he looked at a new picture hanging on Big Mama's wall over the TV of all 10 (yes 10!) of her grown children (hubby is the youngest) taken last year. He counted everyone and said, "Daddy has 10 brothers and sisters." She said yes (yes I know it's 9, but why get technical). So he says, "Big Mama must have had a REALLY big egg!"