Fertilization is a random event with many possible outcomes. To determine the probability that any one sperm will fertilized any particular egg, you multiply the probability of the separate events together. That is, 1 in over 8 million X 1 in over 8 million, which is greater that 1 in over 64 trillion. Any fertilized egg possesses a combination of genes, that is one in over 64 trillion different possible combinations. It is an understatement to say that you are unique, unless of course you have an identical twin.