I was just re-reading my comment and well *knock head on the table*! You are RaeWhit! Sorry, it was written at two in the morning! I just couldn't stop reading and wanting to know what happened. You got me completely surprised with Roger/Justin being James' twin and Harry's father.
I just love Snape (mostly his voice... which are in my head). He's really a fascinating character to imagine, his motive, his character, his mind (and his nose :P)!