TLDR; If we accept that a human being is formed at the “moment of conception” we run into a strange paradox: in some cases this “person” or “soul” splits into multiple “souls” or “persons” a few weeks later.
Most Christians I have met think that human life begins at conception, or the moment the male’s sperm fertilizes the females egg. It is at this moment, during the mixing of genetic material from the two parents that most theologians state the biological entity becomes a “person” or “human being” with its own soul.
Yet something strange happens in the next two weeks, this “human being” can then split to form two seperate fetueses. For you see, the process of Monozygotic Twinning (the biological act of creating twins) happens up to two weeks *after* the theologians say the fetus has a soul.
Does this mean that a second soul is then added to the fetus? (Which body does the first soul stay in?
Does this mean the original soul is split in two?
These are fascinating theological and philosophical questions that serve as reminders: things are not always as simple as they appear.