This always fascinated me, that you get to a point as a couple were you almost blend together and stop being and individual.
Well, some dude dedicated an entire website to it, and is planning to publish a book with the stories that go along with it. http://www.jut-en-jul.nl/
I knew this couple, they were both freshman at the time, so about 19 yrs old.
They walked into church one day and were wearing matching striped shirts (like the big thick stripes you would see on Rugby players) and not only was it the same color, etc. It was such that the lines lined up when they sat next to each other as if they were wearing one big shirt.