Perhaps your 'confusion' is centered around the very astonishing difference between an ORGANISM and mere subunits of an organ (the gamete producing organs called sex organs) which are subunits of an organism. When the chromosomes of the ovum and the chromosomes of the spermatazoon combine to form the normal complement of human chromosomes for a human organism, the subunits have become an organism, a human organism, a human at earliest age in the lifetime begun at conception.
BTW, thanks for the ping, Kevin.
It’s not as simple as that. Human life does not have a sharp beginning, as does individual existence. The chain of life is unbroken, for each human to be born.