Starting from the second half of the twentieth century there have been dramatic changes in the family formation pathways in most Western countries (Buchmann and Kriesi 2011; Lesthaeghe 2010; Shanahan 2000). Pathways have become less standard and more diverse, with increases in unmarried cohabitation, childbirth within unmarried couples, and separation and divorce (Brückner and Mayer 2004). These new family behaviors have spread across all social strata (Lesthaeghe 2010). Some suggest that family formation patterns have been increasingly shaped by individual preferences, resulting in a ‘choice biography’(Giddens 1991; Woodman 2009). Others claim that there is a diverging pattern in family formation between those of high and low socio-economic class. McLanahan (2004) describes how lower educated women are increasingly likely to become single parents compared with highly educated women in the United States, in what she calls “Diverging Destinies”. Perelli-Harris and colleagues (Perelli-Harris and Gerber 2011; Perelli-Harris et al. 2010) argue that many family behaviors in Europe are not the result of individual choice, but of structural constraints, and they describe for instance the increasing rate of childbearing within cohabitation rather than marriage as a result of a “Pattern of Disadvantage”. Thus, there is some debate to what extent the new diverse set of family formation patterns are the result of cultural changes in individual preferences or the result of changes in structural conditions. In this chapter I will focus on the influence of socio-economic background on family formation behavior and disadvantage in young adulthood, drawing on results