Most recently, the role of grandmothers has been highlighted as significant in the lives of their grandchildren in South Africa. Studies have previously highlighted the contribution the Old Age Grant makes in contexts of poverty, orphanhood and the migrant labour system. Similarly, studies on the Child Support Grant (CSG) have illustrated its contribution to the well-being of children and families in general. However, missing in these examinations has been an understanding of how the CSG is contested in contexts of parental absence due to internal labour migration. Through a thematic content analysis of qualitative interviews with members of migrants’ families, this article illustrates that in the context of internal labour migration, family responsibilities shift in ways that make unemployed grandmothers who do not receive the Old Age Grant vulnerable. This vulnerability is manifested through a tension in familial relationships. This tension stem from the contestation of the CSG by young labour-migrant mothers, the guardian (grandmother), and the beneficiaries of the CSG. The article concludes that these tensions result from continuing socio-economic struggles experienced by poor households.