The Case of the Serial Sperm Donor One man, hundreds of children and a burning question: Why? Credit...Keith Negley In 2015, Vanessa van Ewijk, a carpenter in the Netherlands, decided that she wanted to have a child. She was 34 and single, and so, like many women, she sought out a sperm donor. She considered conceiving through a fertility clinic, but the cost was prohibitive for her. Instead, she found an ideal candidate through a website called Desire for a Child, one of a growing number of online sperm markets that match candidate donors directly with potential recipients. Ms. van Ewijk was drawn to one profile in particular, that of Jonathan Jacob Meijer, a Dutch musician in his 30s.