This data brief gives an overview of the background, design, and content of the multi-actor OKiN survey (Ouders en Kinderen in Nederland; Parents and Children in The Netherlands). The purpose of OKiN is to examine the individual consequences of family complexity for intergenerational relations, intergenerational reproduction, and individual health and well-being. Another goal of OKiN is to generate detailed and nationally representative descriptive information on the types and degrees of family complexity that contemporary adult generations in The Netherlands (adults born between 1971 and 1991) have experienced when they were growing up. Unique features of the OKiN data are (i) the oversample of persons who grew up with separated and/or widowed parents, and persons who grew up with a step-parent; (ii) the double multi-actor design (i.e. primary respondents (anchors) report about multiple parent figures and parent figures (alters) report about multiple children); and (iii) the systematic probing of relations to and characteristics of all parent figures in the respondent’s life. The brief provides the first descriptive findings about the OKiN respondents.