My sibling, my child

In the past when an unmarried girl became pregnant, her parents often raised the baby as their own. The 'real' mother would be treated as a sibling of her offspring. The child might not realise until many years later. Not surprisingly, where these secrets are kept, they can be immensely destructive.

We can be glad that in many parts of the world, these lies and deceptions are no longer necessary. But if the stigma of unwed motherhood has dwindled, the opportunities for blurred family boundaries have not. With the advent of IVF, embryos can be created and stored in laboratories, sometimes for many years. If and when they are transferred to a uterus, it could in theory be anyone's uterus.

IVF embryos are usually transferred to the uterus of their mother. But what if she is – instead, or also – their twin sister? This is the scenario conjured up by Michel Janse, herself an IVF baby born in 1996 from a 'batch' of embryos created by her parents. Michel has shared on her Tik Tok channel that she regards these embryos as her twins. (Perhaps quadruplets or quintuplets would be more accurate, depending on how many there are, but I refer to 'twins' for simplicity here.)

IVF enables us to fragment many aspects of reproductive biology in ways that raise new questions. Michel shares the date of her conception with the frozen embryos, and with her existing younger sister. But neither that sister nor any of the remaining embryos share a date of birth with Michel. Should we still use the term twins in such a case? Or simply siblings? The answer is open to interpretation. What is evident is that Michel feels there is something significant in the relationship between herself and these embryos. She feels connected with them, and is struck by what she perceives to be the randomness with which fate has decreed that she and her sister were plucked out to be born, while they remain frozen.

Perhaps many adults in Michel's situation muse over the same themes. But Michel has taken her musing a step further: she has spoken about the prospect of having one of these embryos transferred to her own uterus. There is nothing very unusual about a woman using donated embryos in order to achieve motherhood, but the idea of a woman giving birth to her own brother (Michel expresses a preference for a boy) may be difficult to countenance.

There are many taboos attached to human family relationships and reproduction. In some cases, we can ascribe this at some level to a form of risk aversion. For example, the taboo against marrying close relatives might arise from the knowledge that the children of such unions are more likely to suffer from genetic diseases. In other cases, taboos arise from strong social, cultural and religious convictions.

Michel does not intend to reproduce with her brother, but to (re)produce him, so to speak. Thus, the taboo pertaining to genetic risk does not apply here. But the interweaving of family relationships may still leave us feeling uncomfortable. Are there any grounds for this other than mere gut reaction? It is important that we reflect on these questions, because they are likely to occur increasingly in the future. As more people rely on IVF and assisted reproductive technologies, increasing numbers of embryos are kept in storage. Where the original parents are happy to donate them to others, should there be any restrictions on who has access?

If genetic relationships count for anything, perhaps embryos' adult siblings, such as Michel, should have a stronger claim than other, unrelated adults. Michel could, uncontroversially, seek unrelated donor embryos for her reproductive plans. But it is not clear why should she do so if she could have a child genetically related to her and at the same time bring one of her siblings into existence.

It is widely recognised that many people have a strong interest in becoming parents. Having a child to care for is not the sole aim; the biological relationship also matters to them. Could it be that people likewise have an interest in having biological siblings? Ordinarily, children are not in a position to exercise this interest. But this does not mean it doesn't exist. IVF now offers that possibility.

However, IVF is usually construed as a medical need generated by infertility, rather than as a means of meeting people's interests, per se. Arguably Michel's parents needed these embryos in a way that Michel does not, at least as far as we know. Yet treatments such as IVF do not cure infertility, nor do they aim to do so. IVF aims to create individuals who will fulfil complex biological and social relationship aspirations held by the prospective parent. Viewed in this way, it is not so clear that Michel's proposal is as outrageous as it might first appear.