There are eight billion people living on the Earth. Can someone have a replica of your face :a doppelganger  ??  There are special cells in our brain known as facial recognition neurons that becomes active only when we see faces. These special cells helps us to study the geometry of the face with respect to one another that is almost identical, but the fact is even the specific features like the eyebrows and the tip of the nose are different. There are different neurons  recognising different facial features even the minutes  one. There are certain neurons that fire for eyes, other for a mouth or a nose, this combination of nerves firing creates a map or a code called a facial scheme.

Our brain perceives face as a geometrical pattern and not as a picture.  Due to our habit of recognising patterns we can see a face even if it's not there if one of those stored patterns in our brain show up somewhere unexpectedly. This effect is called pareidolia. We sometimes get fooled because our brain don't pay attention to the details of faces. The more time we spend with people the better we can tell their face in comparison to others, because our face software gets help from our long term memory. But if one don't know two people they are most likely to think that they look alike. Researchers at Cambridge University developed a face memory test that anyone can take. Some people are Just better than others at facial recognition and scientists are yet to find answer to this. They are probably able to sense details in their face patterns that others can't.

 Our face is just as unique as a finger print or as DNA and there are professionals who can study these uniqueness. If police need to identify someone from an image they turn to professional forensic anthropologists specialising in facial anatomy. If we consider just eight facial measurements the odds of people having the same faces are about one in a trillion which is impossible to claim that there's a carbon copy of your face. People may look similar to you due to similar positioning of eyes, nose, eyebrows, lips and other facial features but if any expert analysis them closely they can easily tell the difference between the two. So everyone's face is as unique as their finger prints or as their DNA.