This article reviews the way that ideas about children's right to know the identity of their biological parents have developed over the last 15 years. It argues that the concept of a child's ‘right to knowledge of origins' is being taken too far, too fast. Although adopted children may certainly benefit from information about their biological parents, the article questions whether it is appropriate to assume this to be the case for all other groups, such as donor conceived children. It expresses concern that full legal acknowledgement of all children's right to know their origins would lead to laws involving significant invasions of individual privacy.