The current understandings and practices related to biological and social fatherhood raise a crucial legal question about which model of fatherhood determination should be adapted to contemporary society: the model of a biological or social father bearing the rights and obligations related to the child. The general ideologies of being a father and the application of different approaches have been analysed comparatively, also trying to provide the best legal policy to consider when interpreting the rules of parenthood in Estonian Family Law Act and the Estonian legal practice. The paper considers the emerging legal concept of social fatherhood to be an inevitable prerequisite for protection of the interest of the child.