Family life in Nairobi has undergone some major transformation in the recent past as a result of the changes in the wider socio-cultural-economic systems. This transformation has had adverse consequences for children who depend primarily or solely on one parent for care, protection and livelihood. This paper examines such changes in the specific salient features of the family system in Kenya and discusses the implications for the well-being of urban children, particularly those living in difficult and deprived circumstances in the slums of Nairobi. What emerges from the analyses is a situation in which changes in the structure and function of the family unit have generated conflicting conceptions of mutual kinship obligation. Such trends have led to the erosion of vital social support systems in the family and community and worsened the condition of many Nairobi children from poor families. The slowing economic growth and deteriorating social infrastructure have also heightened the level of deprivation and marginalization of the urban poor, particularly the children.