Seventeen years ago, when she was in her thirties, Cindy and her female partner decided they wanted to have children.

The couple spent hours pouring over sperm donor profiles, finally settling on an anonymous man with a clean medical record and few health issues in his family. He was an anonymous donor, and they knew him only by his identifying number.

Cindy gave birth to a healthy baby boy. Eventually the couple used the same donor to conceive again — and soon enough they were raising two boys.

When they were older, the boys found some of their half-siblings by entering the sperm donor’s number into an online database. Eventually the parents of the half-siblings decided to have them all take DNA tests.