This study explores how donor-conceived adults experience pre- and post-disclosure intra-familial dynamics of knowledge and ignorance in relation to their means of conception. Data were collected through an online survey of 59 individuals aged 21–46 years, who were recruited through the German support and advocacy group Verein Spenderkinder (the Association of Donor-conceived Children). Participants were born into families with heterosexual parents and learned about their conception via anonymous sperm donation between 5 and 46 years of age. Thematic qualitative text analysis revealed four main themes regarding the challenges donor-conceived adults face in reconciling their sense of identity and their relationships within the family: non-absoluteness of pre-disclosure ignorance, new fields of ignorance emerging post-disclosure, ways of dealing with the newly acquired knowledge, and conflicting ownership claims on knowledge and ignorance. These challenges pertain not only to knowledge and ignorance of the participants’ means of conception but also to the way in which (non-)knowing is perceived and managed by family members. Utilizing Peter Wehling’s taxonomy of ignorance as a theoretical framework, the study argues that intra-familial conflicts and challenges experienced by the participants can be attributed to either shifts in or stakeholders’ colliding claims to control the epistemic, social, and temporal dimensions of (non-)knowing in relation to the participants being donor-conceived.