Drawing on in-depth interviews with caregivers of left-behind children (LBC) in rural China, this article seeks to explore their understanding of migration motives and the social process of taking on care-giving roles for LBC. The authors argue that there are underlying socio-cultural explanations pertaining to economic motives for migration; such as, making contributions to social events (weddings and funerals) in village life, and fulfilling social obligations for left-behind sons' futures. Parents migrate to save for sons', but not daughters', adult lives. Grandparents, particularly on the paternal side, are expected to fulfil social obligations to care for left-behind grandchildren, even without immediate financial returns. These suggest that left-behind boys, and in particular boys cared for by paternal grandparents, may be at greater risk than other LBC, as they may receive even fewer resources in the form of remittances from migrant parents in their early childhood.