This dissertation consists of an introductory chapter; three quantitative papers, all using data from the Fragile Families and Child Wellbeing Study; and a discussion chapter. Chapter Two, “For us or the children: Exploring the association between coparenting trajectories and parental commitment,” is situated in commitment theory and estimates latent growth curves. Findings suggest that coparenting relationships among unmarried parents are strong across the first five years of their children’s lives. Further, coparenting relationships appear to influence parental commitment at year 5. Supportive coparenting among unmarried, cohabiting parents (i.e., less committed than married parents) increases the strength of parental relationships.

Chapter Three, titled “Maternal partnership transitions and coresidence with extended kin,” is situated in life course theory and estimates fixed and random effects models. Findings suggest that unmarried mothers versus married mothers are significantly more likely to coreside with extended kin, especially early in their children’s lives and following a partnership break up. Unmarried mothers, versus married mothers, are significantly more likely to live in extended kin homes than their own homes. By year 9, unmarried mothers are significantly more likely to live elsewhere—either with friends or in temporary shelters. Reliance on extended kin appears to weaken over time, which may be associated with mothers experiencing more stress when living with family, or because mothers have exhausted the resources available to them from extended kin. Race is a more significant predictor of extended kin coresidence than socioeconomic status, with significant associations between Hispanic and mothers who self-identify as “other” races and extended kin coresidence. Importantly, this study found that money is not the only significant factor among families who double up; rather, mothers turn to family members during transitional times.

Chapter Four, “Nest effects: How children fare when changes occur within their mesosystems,” is situated in ecological theory and estimates multilevel models. Findings suggest that extended kin mediate the association between mothers’ relationship transitions when mothers consistently cohabit, when they transition from cohabiting relationships to being single, and when they are consistently single. Although extended kin coresidence appears to increase both internalizing and externalizing behaviors, they do buffer children from instability caused by fathers’ incarceration or mothers’ new multipartnered fertility. Extended kin may offer resources (e.g., attention) to children when their parents are distracted or absent. Children who visit fathers and who benefit from fathers’ child support payments fare better than children who do not. Race and education appear to moderate the association between family structure transitions and child wellbeing. For nonwhite children, living with extended kin and mothers’ relationship transitions increase children’s internalizing and externalizing behaviors. On the other hand, if nonwhite children live with extended kin, but their parents do not experience a transition, extended kin do not influence externalizing behaviors. Mothers’ education levels influence child wellbeing; however, for the lowest educated mothers with no transitions, extended kin coresidence appears to buffer children from externalizing, but not internalizing behaviors. Overall, children of mothers with less education, net of extended kin coresidence and transitions, are more likely than children with higher educated mothers to express internalizing and externalizing behaviors.

Chapter Five explores the connections between the three quantitative papers, discusses the contribution each makes to the literature, and highlights future research. These three papers connect in that mothers’ relationship status is an important factor in coparenting relationships (see Fagan and Palkovitz 2011) doubling up (Pilkauskas et al. 2014), and child outcomes (Lee and McLanahan 2015). There is evidence that a “new package deal” exists, suggesting that parents are initially committed to their shared children rather than to each other. However, if parental commitment (to each other) increases, parents may prioritize their relationship over their children (even briefly)—which may explain why mothers’ reports of children’s internalizing and externalizing behaviors increase when they move in with, or marry, biological fathers. However, many mothers break up with both biological and social fathers over the first nine years of their children’s lives. Relationship transitions may necessitate a period of coresidence with extended kin. Extended kin coresidence exacerbates maternal stress (Jackson 1998) and makes things worse for children—which may be why mothers tend to rely less on extended kin as their children age. Family members may interfere too much in mothers’ lives, both to protect mothers (and their children) and themselves. In other words, extended kin may interfere in mothers’ relationship decisions when mothers have supportive partners, as extended kin may benefit from mothers’ partnerships (i.e., extended kin may not be providing support to mothers when they are partnered). Although extended kin make things worse for mothers and their children, they do mediate the association between paternal incarceration and mothers’ new multipartnered fertility. As focal children deal with changes in their mesosystems, extended kin may provide support (e.g., attention, financial support) that buffers children from change.