Care and socialization between siblings – referred to as sibling care – is a social phenomenon in western pluralistic societies that for several reasons remains invisible. An important reason is that most studies of sibling relationships take place in research groups from similar socio-cultural backgrounds, i.e. white urban middle class with small families. By comparing sibling care in three groups in the Netherlands from diverse backgrounds, that is migrant (Turkish-Dutch), large families in a religious conservative fishing community (Urker-Dutch), and urban (Metropolitan-Dutch) the research aims to show diversity. Sibling care also lacks a clear picture; socialization processes between siblings have not been sufficiently described. Therefore, the study follows a qualitative approach from the perspective of siblings themselves and involves 19 women and 15 men, all young adult firstborns. The central question is: What variations exist in the perspective on sibling care of young adult firstborns in families with a Metropolitan, Urker, and Turkish background in the Netherlands? In chapter 1 (Introduction) the different choices are accounted for. Chapter 2 (Problem analysis) gives an overview of various categories of sibling roles in relation to sibling care. In particular four categories of sibling care: support, regulation, supervision, and modeling are highlighted.Next to characteristics of the relationship between siblings (age, birth order, gender) the socio-cultural context of the nuclear and extended family is considered, as are variations in cultural norms regulating sibling role responsibilities and behaviors. Chapter 3 (Methods) describes the qualitative methodology in more detail.Chapter 4 covers the findings of the study comparatively. Chapter 5 discusses the findings and draws conclusions. Both chapters cover variations in five specific subjects: the socio-cultural context in which the respondents grew up; contact and joint activities between siblings; cultural views on sibling and gender roles; ...