The old word I heard was "Doppleganger", though if you say that here in Germany, people look at you like you are speaking Chinese...
Rowan and I were waiting at a tram-stop a few months ago when we saw this poster...both of us stopped and stared... Rowan turned to me and said: "Look! It's Uncle Rob!"....
Look at the teeth Kate- it's like Rob's teeth if he'd worn braces!
