This entry describes the growing phenomenon of contact among families who share the same sperm donor. Lesbian, bisexual, transgender, and queer (LBTQ) parents, as well as sperm donor-conceived children, adolescents, and adults, can use registries at donor insemination (DI) programs or independently established by parents to contact others who have the same sperm donor. The entry reviews research about experiences among people who share the same donor—who are “donor-linked”—and why they might want to contact each other. As research to date is primarily quantitative, this entry also includes more in-depth findings about one set of donor-linked families. These families’ experiences provide insight into the complexity of this new phenomenon and the difficulties with defining their relationships.