It is a scientific fact that every person is unique; also unrepeatable. Even identical siblings have distinct personalities. This is due to their having unique souls. It is no different for the smallest persons. Each one, from his conception and first moments as a zygote (or single cell), has an individual soul and the entire genetic code throughout him to develop into a grown human person. He just needs nourishing from his expectant mother. This is a marvel of God’s Creation!