Ties van der Meer confronts an inheritance that extends far beyond his own biology. At 47, he remains uncertain about the number of his half-siblings, a consequence of anonymity protections that preceded modern DNA testing. The Dutch fertility clinic where he was conceived destroyed donor records after the Netherlands banned anonymous donation in 2004, erasing any path to genetic relatives.

This personal uncertainty now fuels a broader policy debate. The European Society of Human Reproduction and Embryology has called for limits on sperm donation, pushing back against the biological consequences of unchecked fertility treatments. The organization's position reflects growing tension between donor privacy and children's right to know their genetic heritage.

The core problem is straightforward. Anonymous donors can father dozens or hundreds of children across multiple clinics. In some European countries, one donor has fathered over 100 children, creating complex genetic networks unknown to families. When these half-siblings later meet through DNA testing services like 23andMe, they discover unexpected connections. Some report shock at discovering they have 30 or 40 half-siblings.

The European fertility group proposes concrete measures: limiting the number of offspring per donor and requiring donor identification systems that allow children access to genetic information upon reaching adulthood. These rules protect donor privacy during their lifetime while ensuring that biological offspring gain critical health and identity information later.

The Netherlands already moved in this direction after 2004, but earlier cases like van der Meer's slip through the gaps. Older anonymous donors and destroyed records mean many never learn their genetic origins. Other European nations maintain looser standards, allowing anonymous donation to continue.

This debate extends beyond emotions about kinship. Genetic information directly impacts medical care. Half-siblings should know shared hereditary risks. Rare genetic conditions may cluster within donor cohorts, information that affects preventive health decisions.

The fertility industry resists stricter limits, arguing they