Historically, paternity has been constructed on the basis of uncertainty. Men and fathers have been underrepresented in studies of reproductive processes and parenting. In adoption, the figure of the birth father has been invisibilized and stereotyped. As part of a qualitative study of origins, identity, and adoption, carried out in Chile, the narratives about their birth father of adults, who had been adopted and sought their origins, were analyzed. The results show that (a) most interviewees had not thought to seek their birth father because they assumed he "did not exist"; (b) information about him is mediated by the birth mother, who acts as a gatekeeper; and (c) when the figure is present, it is usually depersonalized as genetic material or personalized negatively. The birth father omission in the adoption process poses challenges for both past and contemporary adoptions, in which birth fathers are ever more visible and heterogeneous.