I shared our news with the in-laws 6 year old. Conversation like this:
Me: Auntie is going to have another baby.
6: How do you know?
Me: I went to the doctor.
6: Oh. So does that mean I am getting another cousin.
6: (exasperated) I have sooooooo many cousins now.*
Cut to the end of conversation, as joined by my husband:
6: Does Uncle know?
6: How does he know?
DH: I was there.
6: (quizzical look)
Me: (exasperated - like I want to explain the facts of life to a 6 year old) He came to the doctor with me.
*6 doesn't have any other actual cousins (living), however, does have a number of second and third cousins that are referred to as cousins.