In response to difficulties faced by families in caring for the aged, the government of Taiwan launched a foreign live-in caregiver programme in 1992. This paper draws upon literature on family, domestic work and motives for caregiving to examine how the long-term co-residence of migrant live-in elder care-workers reconfigures Taiwanese families. Our analysis, based on in-depth interviews conducted in the summer of 2009 with 20 Vietnamese migrant live-in care-workers, uses the concept of ‘social family’ to document the close emotional and quasi-familial relationships between foreign care-workers and members of Taiwanese families. Narratives shed light on the dynamics of these relationships and show the limitations of the concept. The inherent asymmetrical employer-employee power relationship remains, while workers constantly negotiate contradictory feelings and positions in the intimate sphere of the employers’ private homes. This paper emphasizes the mutual dependency that migrants experience as both workers and members of a new family. Rather than being seen as cheap, disposable labour, migrants become indispensable to the families. It is this dependency and intimacy that make them part of the family, but also continues to make them vulnerable to abuse.