This study examines whether and how couples share the provision of informal care for their parents. Four waves of the British General Household Survey contain cross-sectional information about caring for parents and parents-in-law. Descriptive and multivariate analyses were conducted on 2214 couples that provided parent care. The findings emphasise married men's contribution to informal caring for the parental generation and at the same time demonstrate the limits of their involvement. Spouses share many parts of their care-giving but this arrangement is less common with respect to personal and physical care. The more care is required the more likely are people to participate in care for their parents-in-law. More sons-in-law than daughters-in-law provide care but, once involved, daughters-in-law provide on average more hours of care than sons-in-law. Own full-time employment reduces both men's and women's caring for their parents-in-law, and men's caring drops further if their wife is not in the labour market. The findings suggest that daughters-in-law often take direct responsibility whereas sons-in-laws' care-giving depends more on their wives' involvement. Children-in-laws' informal care-giving might decrease in the future because of women's increasing involvement in the labour market and rising levels of non-marital cohabitation in mid-life.