I have. It's not a very comfortable experience..actually its very awkward to say the least.
You remember that Friends episode where Joey meets his hand twin? Well the exact same thing happened to me. I was looking at my brother's girlfriend's hands and I couldn't get over the fact her hands are the same size as mine..even right down to the veins and placement of veins on her hands.
So I put my hand against hers just to make sure I wasn't imagining this and yep..we have the same hands. I wonder how my brother feels about this?
I guess thats not my doppleganger but it still freaks me out.
How about you guys?