The Soul of the Matter: A Theological Problem

This is a problem for Catholic theology.

In 2002, Lydia Fairchild, a mother from Washington State, faced a baffling and distressing situation when DNA tests required for public assistance showed she was not the biological mother of her two children—despite having physically given birth to them. The results raised suspicion of fraud or surrogacy, and authorities even considered removing her children from her custody. When she gave birth to her third child in a hospital under supervision, the same outcome occurred: DNA tests again claimed she was not the mother.

Fairchild’s legal battle intensified, and she stood on the verge of losing her children based on genetic evidence alone. Her attorney, Alan Tindell, began researching unusual biological conditions and came across a similar case involving a woman named Karen Keegan. This led to the discovery that Lydia was a chimera—a person with two sets of DNA. In her case, it was caused by absorbing a fraternal twin in the womb.

A cervical DNA test finally matched her children's DNA, confirming her biological relationship to them. This critical breakthrough not only saved Lydia’s family but also raised important concerns about the reliability of DNA evidence in legal settings. Her case became a landmark example of how rare genetic conditions like chimerism can challenge long-standing scientific and legal assumptions.

Lydia absorbed her twin. The first and most obvious theological question: what happens to the soul infused at conception? 

Different reproductive tract vs somatic DNA raises the question of whose DNA she is transmitting when she has children. Is the different DNA considered hers by right of conquest, for having essentially eaten her twin in the womb? This is not an isolated problem. About 8% of fraternal twins could end up with blood chimerism. In the case of triplets, the chance for blood chimerism rises up to 21%. True tetragametic chimerism (such as Lydia's case) is believed to be rare, with only 100 documented cases in the medical literature, but it may be more common than once believed. It is possible that up to 10% of singleton births may have started as twin pregnancies.

Lydia's case is a less obvious form of the even more pressing problem presented by Abby and Brittany Hensel, conjoined twins who share a common torso and common reproductive tract. Abby Hensel, one of the conjoined twins, married Josh Bowling. Now, the only difference between Lydia Fairchild and the Hensels is the latter has two fully developed brains. But, as noted, the Hensels do share a common reproductive tract.

So, if it was licit for Lydia to conceive, carry and give birth to children that do not share her DNA, then why would it not be licit for the Hensels to have children, especially since Abby and Brittany have the same DNA? In what sense is the Hensels' marriage valid, given that the two were already conjoined into one body, so that both women are having sex with one man, but only one of those women is married to that man? Is the other woman always committing adultery? Or is Josh actually married to both women? 

But if the Hensel's marriage is invalid, then in what sense is Lydia Fairchild's marriage valid? Unlike the Hensels, Lydia's reproductive tract is actually someone else's body. Now, true, the other body belongs to someone who is not ensouled and alive, as far as we know, but her reproductive tract is certainly not "hers" in the same way her somatic cells are "hers", are they? If we argue that a baby in the womb is someone else's body because of DNA, then Lydia's reproductive tract is also someone else's body because of DNA. If we argue that her reproductive tract belongs to her, then the baby in the womb also belongs to her in very much the same way, and the somatic argument against abortion collapses.

But, if we try to keep the pro-life somatic argument alive, and insist her reproductive tract is not hers because of its different DNA, then is having sex and conceiving with Lydia a form of necrophilia? The organs are alive, but the soul that animates the DNA is not the original infused soul, again, as far as we know. When a person dies (that is, when a person's soul separates from the body), individual organs within the corpse can stay alive for hours or even days. This is what allows for organ transplant. If we argue that the soul of Lydia's twin has departed, then Lydia's body has just kept her deceased twin's body on "life support" for Lydia's entire life. Thus, a strong argument can be made that having sex with Lydia really is really just necrophilia with her dead twin. The Catholic Church does not permit necrophilia. 

So, can marriage with a true tetragametic chimera be valid? Under what circumstances? And how would you know that you married a chimera if no DNA testing has been done? Is that grounds for an annulment? 

The Catholic Church isn't equipped to deal with this.