Misattributed paternity unsettles fatherhood because biological exclusion does not erase the relational history of care, provision, naming, kin recognition and attachment formed through the prior belief that a man was the child's biological father. This article argues that the central injury is the distortion of relational agency: a man fathers, provides and locates himself in kinship through information that later proves materially false. Drawing on South African fatherhood scholarship, kinship anthropology, bioethical writing on misattributed paternity, and legal-text analysis of the Constitution, the Children's Act 38 of 2005 and selected South African cases, the article develops deceived fatherhood as an injured paternal position and relational justice as the response required after disclosure. The analysis rejects biological absolutism and compulsory social-fatherhood continuity. It argues instead for child-sensitive truth, evidentiary discipline, documentary repair, differentiated redress pathways and voluntary care arrangements that receive paternal injury without converting the child into an instrument of adult retaliation.