You & I have never existed before & will never exist again after our demise. Note that what you & I are is essentially the memories & thought processes in our brains. After our demise those brains will never exist again. Identical twins are not really identical. They have different fingerprints & some other different physical traits like retinal patterns. By adulthood, they have had different experiences & their brains have different memories & different thought patterns. If identical twins are not really identical, how can anyone expect two less related or unrelated people to be identical?