I have a daughter. Her name is Josephine. She is almost a "whole hand!"
Me: Josephine, do you want me to have another baby?
Josephine: Ummm.... No.
Me: What if I had a baby grow in my tummy and then I gave that baby to someone else?
Josephine: Hmmm... Yeah - and maybe Amanda (aunt) can give baby David (newborn cousin) to someone else!
...okay. Not going as planned.
Me: There are some people who can't have babies grow in their tummy. A mommy and a daddy could put their baby in my tummy. It could grow in my tummy and when it comes out, I could give the baby back to it's mommy and daddy.
Josephine: YEAH! THAT'S A GREAT IDEA!
Sweet, sweet girl. And an ongoing conversation.