Security, security…
I can see this happening a lot back in the day because it seemed like security at airports was not really all that great. It probably wouldn’t have been very difficult to get away with using your twins passport. But the way security is after September 11th, 2001, I have an idea that they would have a much more challenging task pulling this off. Besides, how often do you really need a passport. Unless you are a regular international traveler, when do people use these things? Once a year for a vacation abroad maybe?