Children in Tanzania live in a variety of family structures, many of which contain related and unrelated non-parental adults. In this article, I use data from the Rufiji Health and Demographic Surveillance System in Tanzania to examine the role of coresident non-parental adults in childrearing. First, I use quantitative demographic data to investigate the association between kin coresidence and child survival, differentiating by lineage. I also examine the role of unrelated coresident adults. Second, I test whether coresident non-parental adults moderate the association between parental absence and child survival. Finally, I draw from qualitative interview data to investigate childrearing practices and beliefs, with a particular focus on parental absence and kin coresidence. I find that, despite the institutionalization of kin caregiving, coresidence with kin is not beneficial, and kin are unable to compensate for parental absence. The two-parent living arrangement is viewed as ideal, although the reality of childrearing in the setting is complex and fluid. While absent parents try to maintain support of their children, such assistance is insufficient in times of health crisis. Kin care for children with absent parents, but their willingness to assist depends on the reason for the absence.