About thirty plus years ago I used to go for a drink in a local pub, and due to work commitments was unable to go on a group skiing tour that the establishment organised. On arriving at the hotel (I was later told) my drinking buddies were amazed to find me sitting at the bar (of course they headed straight to the bar after five minutes in their rooms - they were my buddies after all!) downing a pint just as I would do so at home. With cat calls and whoops they descended on this poor clown, only to discover it was very much not me - just my apparently identical double who obviously shared some of my proclivities.
Strangely enough, there is another feature of doubles that I think, makes the phenomena even more interesting. In my early twenties there was a band called Squeeze (iirc), whose lead singer was a guy called Glenn Tillbrook. We were said to bear an uncanny resemblance to eachother - but interestingly I have since discovered, it was only at that particular age. Now we look nothing alike at all, and I've seen a photo of him as a child to which I bore no resemblance. So it's like for a brief period your ongoing visage sort of crosses that of someone else, and you momentarily appear almost indistinguishable from each other. I think that's great - and really only to be expected as opposed to the opposite where you are born identical and stay so over the course of your growth and ageing. If this latter happens then it probably is the identical from from whom you were separated at birth.
though most of us could say the same, of ourselves 
wow thats truly amazing .. you could take "yourself" out as your own plus one ... how hilarious would that be????