[He hasn't even realised - more careless jesting for the sake of a joke that seems to have been long forgotten. Now he's just interested in her hypothetical children (children he will never see, hypothetical or not), and doesn't even stop to notice the effort behind that laugh. Out of sight, out of mind, and Fred's certainly out of his mind at the moment. Do try again later.]

You don't mean that. Don't worry, you haven't got to say it. I already know.

[He clears his through, and then he is definitely mimicking her voice.]

"I can hardly imagine any childhood without having a pair of loving and fantastic twins about."