Are you a twin?

Each person is different in some way even if it cannot be seen with the naked eye. Whether it's hair color, eye shape, height, weight etc. These differences in appearance are due to DNA. What if this isn't entirely true? What if we all have a twin? What if there is a person that has similar or the same DNA as us? How can we be so certain that we are ALL unique? This just does not seem realistic. What do you think are the chances of ever meeting this person at some point in your life? I could be just thinking out of the ordinary or we really COULD have a twin out there. THINK ABOUT IT.