Baby Sister

Faithy's been to play at her friends house after school today, her friend has a 6 month old baby brother.
So she as telling me about the baby, and sounded quite enamoured with him, then....
Me: So do you want a baby brother too?
Faith: No I want a baby sister
Me: really?
Faith: yes, so can I have one
Me: no, I can't be bothered making one
Faith: how do you make a baby?
Me: ask your dad
Faith: does he know??