Musings on the Soul

Today I watched a one hour show on the Discovery Health Channel titled, "I Am My Own Twin." Unlike it's channel mate "I Didn't Know I Was Pregnant," this show was not scary. It was just rather interesting. It followed the stories of two completely unrelated women who found out through different life circumstances (one was filing for welfare and had to prove the parentage of her children, the other needed a family match for a kidney transplant) that their DNA did not match that of their children. The show explained how every child has 50% of one parent's DNA and 50% of the others. So there is no way that a woman who gets pregnant and gives birth to a child cannot share that 50% DNA match with the child... or is there? According to their findings, the children of these women could not possibly be the children of these women, though DNA tests revealed that there was some matching to the rest of the mother's family. After years of tests and head-scratching, one doctor had an idea: maybe his patient was a chimera.
The term comes from Greek mythology and is a creature that is part lion, part goat, and part serpent. Obviously these women were NOT liongoatsnakes. When pertaining to humans, the medical term chimera means that two fertilized embryos fused into one at an early stage of the pregnancy and formed one individual. This happens in the first four days of the pregnancy, because if they were to fuse after that time, there would be portions of spinal columns and the result would be Siamese twins. Instead, a chimera is one person, but with two distinct DNAs. Essentially, it is two people in the body of one, twins sharing one space.
Typically, chimeras have outward physical characteristics that clue the doctors in on the existence of the anomaly, but these two women were not typical chimeras. Most chimeras will have odd pigmentation on their skin. Also, if the two fused embryos were opposite genders, the resulting child will be truly hermaphroditic, with one set of DNA being male and the other set being female. In the case of these two women, though, the fused embryos were both female, and had it not been for DNA testing, they would have gone their entire lives without knowing they were their own twin.
The show discussed the possible legal ramifications of chimeras that do not physically show symptoms. One judge talked about the heavy reliance on DNA evidence and wondered if he had ever denied custody based on DNA findings that were actually false. A person could be the physical father, but it is the invisible twin who passed down the genetic material. My deepest thought, though, was a bit different.
You see, all my life I have believed that a person becomes a person at conception. I believe that at that moment, they are endowed with a soul, and that after conception they will never cease to exist. If they are aborted, their little souls will just go right on up to heaven. If they have the good fortune of being born and living a life, then they can reach an age of accountability and have to take the consequences of their actions. Hopefully, they will hear and accept God's Word and then their soul can go to heaven at death. But this is not my point, so let's get back to it. My question is this: If the soul exists at conception, and there are two fertilized embryos in one womb, then there are two souls... well, what if they merge? Do these chimeras, then, have two souls? If not, then when does the soul begin to exist? If they DO have two souls... man, I don't fully understand the implications of that. There are a hundred roads I could go down for that one. I really want feedback on this. What do you think?
To close, this concept of absorbed twins and two entities in one body is not new. I immediately think of a book by Stephen King entitled "The Dark Half." In it, there is a man - a good man, an author with a family - who has a twin living inside of him about which he does not know. But this man experiences blackouts where his evil twin takes over his mind and does evil things with the body in which he also lives. One body. Two souls. Again, write your thoughts.