An extensive literature has documented that individuals raised with more siblings perform less well in school and complete fewer years of education. Interest in the relationship between the number of siblings in one?s family (hereafter sibship size) and developmental outcomes spans across a range of disciplines including demography, economics, psychology, and sociology. The study of the relationship between sibship and education provides insight on the processes by which family resources are mobilized to support children?s education. But, ultimately sibship research documents how children?s access to some family resources can become diluted when the resources support the development of several children. In this dissertation I highlight how sibship size shapes individuals? experiences throughout childhood and young adulthood. The empirical analyses described in this dissertation examine developmental outcomes and educational outcomes from the earliest months of birth to the completion of postsecondary schooling. In doing so, I contribute to several ongoing debates and strands of research within the sibship literature.