Ties van der Meer does not know how many siblings he has. The 47-year-old was conceived at a private fertility clinic in the Netherlands using sperm from an anonymous donor. After the Netherlands banned anonymous donation in 2004, the doctor destroyed records that could have identified the donors. Van der Meer describes the situation as problematic and emphasizes the right of children to know their biological parents. He eventually tracked down one sibling, who helped identify his father and other genetic relatives, but he may have other siblings he will never find. Similar stories abound: some donor-conceived individuals discover they have dozens or even hundreds of half-siblings. One woman who found 25 half-siblings over seven years told the Guardian it made her feel mass-produced.
ESHRE proposes a European limit of 50 families per donor
The European Society of Human Reproduction and Embryology (ESHRE), meeting in London on July 9, 2026, has proposed international limits on the number of children a single donor can father. The plan starts with a limit of 50 families per donor across Europe, eventually decreasing to 15 families. Jackson Kirkman-Brown, professor of reproductive biology at the University of Birmingham, stated that a transnational limit is the only sensible approach, as sperm is often exported across borders. For example, Denmark has a national limit of 12 families but is a major sperm exporter; in the UK, over half of sperm donations in 2020 were imported, mainly from Denmark and the US.
Sponsored Protocol
The Jonathan Meijer case: over 550 children from a single donor
The problem is exemplified by Dutch donor Jonathan Meijer, who started donating in 2007 and whose sperm has been used to conceive between 550 and 600 children. The foundation Stichting Donorkind, chaired by van der Meer, took him to court, and in 2023 he was ordered to stop donating. Such stories are distressing for donor-conceived people and raise concerns: half-siblings might unknowingly form romantic relationships, or a harmful genetic mutation could be passed to many children. Although donor screening is rigorous, a Danish donor with a cancer-causing mutation fathered at least 197 children across Europe, some of whom developed cancer and died.
Sponsored Protocol
Challenges in enforcing international limits and the role of genetic testing
Genetic tests from companies like Ancestry and 23andMe have made it easier for donor-conceived individuals to find genetic relatives, even when donations are anonymous. However, sperm can be frozen for years, leading to posthumous discoveries or siblings of very different ages worldwide. Van der Meer believes even a limit of five families per donor would be high, and for international donations, he suggests a maximum of two families. Still, he calls ESHRE's proposal a positive first step. If limits reduce sperm supply, some may turn to unregulated donations, risking health issues and potential parental rights claims. As van der Meer said, you have to start somewhere.
Sponsored Protocol
For insight into transparency in medical practices, see the article on Anthropic's hidden J-Space inside Claude, an interesting parallel on the importance of understanding internal processes. Additionally, OpenAI's discontinuation of ChatGPT Atlas shows how standards are being reconsidered even in tech. For more on sperm donation, visit Wikipedia's sperm donation page.
