By the late 1980s, as a result of the AIDS crisis, the business of cryobanks was growing; frozen sperm was safer than the fresh sperm that doctors often procured to help infertile couples. The industry continued to develop throughout the 1990s as banks profited from global demand, a rise in single motherhood and the increasing acceptance of gay parenting. With the rise of the internet, banks could market directly to consumers via elaborate websites, advertising not just donors’ assets — their academic credentials, their celebrity-look-alike features, their height — but selling their willingness to be known. At California Cryobank, the standard arrangement allowed for a description of the donor and an answered questionnaire; but for additional fees, purchasers of sperm could also receive a voice recording of an interview and more extensive profiles.

The business might have faltered around 2000, when improved reproductive technology meant that doctors could help more couples conceive, even if the male partner’s sperm count was low. Sperm banks started marketing more aggressively to single women and lesbian couples (and possibly helping to normalize that parenting in the process).

Around that same time, the first children conceived via sperm donation started coming of age, people whose eventual agency and powerful curiosity the sperm banks and even the parents hadn’t fully considered. For many of those children, trying to reach out to their anonymous sperm donor was an exercise in frustration. “California Cryobank’s policy has always been to attempt to facilitate donor contact upon request of any 18-year-old offspring,” Scott Brown, vice president of communications for the bank, said. In fact, he later clarified, the effort to contact the donor often started — and ended — with a letter to the donor asking for an update of medical records. Only if the donor responded and re-established contact with the bank would he then learn that a biological child was trying to reach him, which meant that both he and his biological child were often left in the dark about who wanted what. The possibility of making that connection was over before it started.

What the banks did not provide, at that point, was a way to connect half siblings from the same donor. In 2000, Ryan Kramer, a precocious 10-year-old, along with his mother, Wendy Kramer, created what would become the Donor Sibling Registry, a place where children like him could enter their donor numbers, seek out their biological fathers and possibly their biological half siblings. They were following the lead of Jane Mattes, the founder of Single Mothers by Choice, who in the mid-1990s started a forerunner to the registry. “At the time, I didn’t see it as political or feminist, but looking back, we took power into our own hands,” Mattes said in a recent interview. Unlike many infertile couples, these single mothers were hungry for openness because it provided community and family, Mattes says. Today, the Donor Sibling Registry matches about 1,000 people a year, a majority of whom are siblings.

Although the Donor Sibling Registry requires that its users be 18 or have their parents’ permission, any parent who has used a donor can access the site or log onto any one of the sibling registries that various sperm banks have since established for their clients. (California Cryobank’s, for example, opened, in 2004.) Countless parents have reared their children, from birth, with photographic look books of half siblings or regular family reunions. For others, who have come to the registries later in life, they function as online revelation factories, sites where thousands have learned not only that they had half siblings but also that they had, in many cases, dozens of them.

Over time the adoption movement popularized the principle that individuals had a right to know their biological roots, and lesbian couples and single mothers, dominating ever more of the sperm banks’ market, called for greater transparency. In the early 2000s, California Cryobank offered, for a premium fee, an option for parents to choose a donor who agreed not just to be contacted when the offspring turned 18 but to respond in some fashion (though still anonymously if that was his preference).

By 2010, experts in reproductive technology were starting to note that internet searchability, facial-recognition software and the future of DNA testing would soon render anonymity a promise that the sperm banks could no longer keep. Since 2017, California Cryobank has stopped offering anonymity to its new donors. Donors now must agree to reveal their names to their offspring when they turn 18 and to have some form of communication to be mediated, at first, by the bank.