Re: "but HOW did daddy put the baby in your tummy?"
My then 6yo asked why I "ate him". That's how he thinks he got there.
Very cute, but very innocent.
Then he learned about chicken eggs & biology in 3rd grade. So I then explained it in egg & fertilized terms. Does he know EXACTLY how one gets to the other? No. His daddy can handle that one in their sex talk in a few years.
Oh, and just personal pref, but I leave marriage out of making babies talk. You don't NEED to get married to make a baby and I'd hate for a kid to get the impression that sex before marriage CANNOT produce a baby. Marriage is nice, but that's a social status, not a biological status.