Our daughter asked where do babies come from when she watched kittens being born at the age of four.
We told her that God made inside the daddy a special type of seed. Inside the mommy God made a special egg. God created love and when the mommy and daddy love each other in a special way, the seed goes into the mommy and it meets up with the egg and God starts growing the baby inside the mommy.
This was ok for a little while, as she asked questions we added to the story.
Some of her questions were:
Where is the seed in daddy, can I see it?
Does the egg in mommy look like this (pointing to the poached egg on her plate one morning)
How does daddy give the seed to mommy?
Just resist the urge to laugh you young parents
My sister begame pregnant and was not married when our daughter was five, new questions arose, just be prepared in every circumstance to give just enough information that will satisfy them and not too much that will take their innocence away.
We taught our daughter that we have very special parts of our body that are so special that they are to be covered at all times (we used the term the bikini area on a girl, swimming trunks on a boy) and that those parts are to be only touched by her, a doctor if mommy said it is ok, no one else. We told her she is never to afraid to tell us if someone asked her or touched her there, no matter what they said.
Just a tip off the subject. In stores you see kids throwing tantrums all the time, even hitting their parents. I would tell my daughter if someone that she did not know grabbed her she was to scream, but I started thinking about all the kids I see doing that, so we told her if this ever happened she was scream really loud and clear "This is not my daddy, (or mommy) help me" And keep repeating it over and over again. We also told her that if she is lost to go up to a mommy with little kids or an old gramma and tell them she is lost and ask them to help her.
Hope this gives you some ideas