This dissertation aims to address the gap in family research concerning the role of siblings in children’s social development. Firstborns’ interactions with their younger sibling and parenting... Show moreThis dissertation aims to address the gap in family research concerning the role of siblings in children’s social development. Firstborns’ interactions with their younger sibling and parenting towards all children in the family are investigated in a four-year longitudinal study following families with two children from the first birthday of the youngest child. In Chapter 2 the prediction of individual differences in sharing with a younger sibling by family and situational factors was investigated. In Chapter 3 the association between parental sensitivity towards both children and compliance and sharing behavior of the firstborn child was investigated. Chapter 4 focuses on sibling discipline and sibling support during parental limit-setting, and associations with inhibitory control, empathy, and gender. Finally, the effect of birth order on toddlers’ social development was examined with a longitudinal within-family design in Chapter 5. Show less