Watermelon baby

Ryan loves watermelon but a few months ago (now aged 4) he was arguing with his mother that he couldn't eat the seeds (white seeds in seedless watermelon) 'cos he'd have a baby in his belly and she was arguing that he wouldn't.
He came over to me and with a serious face asked, "Nanna, do babies come out of your belly button?" I looked at his Mum who smirked and looked away, his brother (aged 8) said, "they come out of your vagina" and Ryan ignored him. Ryan again said, "do they Nanna? Do they come out of your belly button?" Again I looked at his Mum who smirked and looked away and again Matthew said they come out of your vagina and again Ryan ignored him, so I ran with the conversation.
Me: No they don't come out your belly button. Matthew was right - they come out of a vagina.
Ryan: Do I have a vagina?
Me: No, boys don't have babies so they have doodles (family pet name for penis) and babies can't come out of doodles can they cos they're too skinny, so only girls have vaginas because they have babies.
Ryan: Where they do wee?
Me: Near there but not right there.
Ryan: (with a scrunched up face) Cos we don't want wee on the baby do we Nanna
Me: That's right
Ryan: And not out of your bum
Me: No, not out of your bum
Ryan (scrunching up his face) Cos we don't want a pooey baby do we Nanna?
Me: No, that's right.
Then he went and ate his watermelon - seeds 'n' all!