Liu, JingwenThe drastic demographic and family transitions since the 1970s have raised ongoing discussions about whether older adults fare well socially and psychologically when they are increasingly likely to age alone in the U.S. Based on the social convoy model, the three studies of this dissertation answer this question by extending the focus from the proximal kinship ties to nonkin networks and broader social participation. Particular attention is paid to gender and racial/ethnic differences as demographic and family transitions are experienced unevenly by different social groups. The first study examines how family instability and the deviation from “normative” family trajectories are associated with older adults’ mental health. It found different levels of importance of the structure and instability of family for men and women of different racial/ethnic groups. Moving beyond family and households, the second study explores the substitution effect of extended family, friends, and neighborhoods in the absence of proximal relations. It reveals the “double plight” of Black and Hispanic older adults who may suffer from both a disproportionate exposure to the declining marriage and a lack of supportive distant relations serving as buffer zones in the absence of core kinship ties. The third study disentangles the population-level age and cohort trends of social connectedness, a more comprehensive indicator of individuals’ social wellbeing. It finds distinct intercohort changes in both the overall level of social connectedness and intracohort gender and racial/ethnic disparities. These trends can be partially explained by cohort differences in socioeconomic resources and health. However, societal changes that emphasize the significance of intergenerational solidarity, friendship ties, digital communication, non-religious social participation, and volunteering may play a more significant role. Taken together, this dissertation depicts a mixed picture of different populations who demonstrate varying levels of vulnerability and resilience against the quickly developing society. Therefore, it calls for both the enhancement of social welfare regimes and more positive narratives about unique resilience and strengths for women, racial/ethnic minorities, and socioeconomically disadvantaged older adults.enDissertationSociologyAgingFamilyGenderMental healthRace/EthnicitySocial Connectedness