A birth chart is essentially a blueprint of who you are and we like to think that we are all very unique in our chart, like a fingerprint. But in reality people can share an exact chart. So the question arises:
Since the planetary positions at birth determine your identity does that mean there will be two identical people?
The short answer is: No.
The charts will be the same but a birth chart is not static. It is not a prewritten and exact map of exactly how life will turn out. We still have free will.
It IS an outline of the POTENTIAL that you have when you enter this life.
We all have different experiences in our family and social lives, race, economic situation, gender etc. and all of these factors will influence the way the planets in your chart express themselves. Some areas of your personality may become more or less dominant than others due to life situations we all experience.
A birth chart reading can teach you so much about who you are because it can shine light into the cracks, the parts of yourself that you have lost or forgotten. And by acknowledging they still exist you can continue to grow and flourish into your best and most divine self.