The role of psychological factors for family formation processes has been underexplored in demographic research. However, psychological concepts such as personality, identity, or skills may have become increasingly relevant for family formation processes such as marital behavior, childbearing, or partnership dissolution, in particular in countries with high levels of individualism. This dissertation aims to address this research gap in various ways. First, the dissertation chapters examine the prospective associations between personality and family formation (marriage, fertility, dissolution) (chapters 1 and 2), identity and marriage (chapter 3), and leadership skills and family formation (marriage, fertility) (chapter 4). Second, the potential mediating role of socio-economic status indicators (income, education) for these relationships is explored (chapters 2, 3 and 4). Third, full siblings are compared to each other when applicable in order to control for shared background factors such as genetics or parental background (chapters 2 and 4). For these purposes, different data sources are used including large and representative survey data from Germany (chapter 1), Swedish register data (chapters 2 and 4), and survey data from Finland (chapter 3). Methodologically, a mix of widely used analytical methods have been applied such as event-history analyses, linear probability models, or Poisson regression models including individual and sibling fixed effects. The findings of this thesis suggest that psychological factors shape family formation processes across the selected European countries (Germany, Sweden, Finland) with high levels of individualism. Personality factors linked to social abilities (extraversion, social maturity, agreeableness) generally show positive associations with childbearing (chapters 1 and 2) and the probability to get married, and negative correlations with dissolution processes (chapter 2). Emotional stability is also positively associated with family formation processes (marriage, fertility), and negatively linked with partnership dissolution (chapter 2). However, these associations only relate to patterns for males whereas females do either not show clear associations (chapter 1), or had to be neglected based on data restrictions (chapter 2). Furthermore, certainty and commitment with future life plans (as indicator for identity) are positively linked with marriage risks over time (chapter 3). Regarding leadership skills (LS), as one specific type of skills, similar associations to personality effects from study 1 and 2 have been found, i.e. LS are positively correlated with marriage and fertility (chapter 4). The mediating effects of income and education, are relatively small for all associations so that future research may examine the role of other potential mechanisms such as intentions, attitudes, or health. Additionally, sibling fixed effects approaches do not show large difference compared to the patterns that are described above.