...well, it's not like Severus has never been in dangerous situations where he had to pretend to be someone he's not, is it?
Actually, with that "Look at me," I wondered if Harry actually knew. Even if he doesn't, I don't suppose Severus would find it difficult to fool him, given how smart he is, the excuse of the war and life-changing events, and his intimate knowledge of Harry. And over time, I think there would be less pretending, anyway.
But to fool parents and siblings? I'd know in the space of one conversation if someone were impersonating one of my family. I suppose Severus does have the advantage of Legilimency, though. Hm, okay, I think he could pull it off. And even be happy, in his Snape-ish way.
Obviously he'd want Lily as a name for their daughter. I'm a little unconvinced that he'd name their firstborn James, though.
This story clearly made me think. :) I must needs read your other work, now. Thanks for the great read!