Once upon a time I think we all knew what “twins” were. They were kids born to the same woman at the same time. With a few notable exceptions (Hercules, for instance, who was the result of a phenomenon called “superfecundation“), this means that twins were 1) conceived at the same time, 2) had the same genetic parents, 3) were in utero together and 4) had the same birthday.
ART, however, has severed the links between these factors and thus left the definition of twins open to new variations. Two years ago I wrote about “twiblings.” These were two kids conceived in vitro at the same time using gametes from the same two people. As embryos they were transferred into two different uteruses. They were born five days apart. They meet some of the criteria for twins (1, 2 and nearly 4) but not all, and so they were described as twiblings.
Now comes this story, which you will notice is entitled “Twins Born Five Years Apart.” Reuben and Floren Blake were conceived via IVF at the same time using the same batches of gametes. Jody Blake gave birth to Reuben in December, 2006 while the leftover embryos were stored in a freezer. Now five years later, using those frozen embryos, Jody Blake has given birth to Floren.
Reuben and Floren meet criteria 1 and 2 for twins. In addition, unlike the twiblings, they were born to the same woman but they were not in utero together and were not born at anything like the same time. Are they more or less related than the twiblings?
This is an opportunity to think about how we use language. It is clear to me that Reuben and Floren are siblings in all the senses I understand. But are they twins? What is it that makes twins a special subset of siblings or, to put it slightly differently, what sets twins apart from siblings?
I think the real question becomes whether these children can claim twindom by virtue of the timing of their conception. For in all other regards they really are just siblings. (I do not mean to disparage siblings, by the way. Nothing wrong with being siblings.)
So are they twins? Does the common time of conception count?
It seems to me the answer should be “no.” The time of conception seems to me quite irrelevant to the experiences of these children. There’s always a bit of mystery surrounding twins–a special language they develop or a special relationship they manifest. But I think this is most likely a product of growing up together–same age/same home. Perhaps, too, the shared in utero experience contributes. (All the stuff about the new science of origins would be common to those in utero together.) Neither is present here.
One challenge of ART, it seems to me, is that it fragments the experience of conception/pregnancy/birth/child rearing in ways that are really new to us. This requires us to think about which things matter for what purposes. I wouldn’t call these kids twins, but perhaps it just made a good headline.
One final thought: If they are twins, then this tells us time of conception is crucial and so perhaps we need a new measure of age–counting from when you were conceived. Reuben and Floren would then be the same age with Floren being five years older than her date of birth suggests. It doesn’t make much sense to me to do this, but it would seem to follow from putting such weight on time of conception.