The assumption of individualised rationality runs through the two dominant theorisations of family behaviour – new household economics and individualisation. We demonstrate the inaccuracy of this assumption, using the results of two CAVA projects into mothers' perceptions and choices in combining mothering with paid work, in allocating tasks with partners, and in choosing childcare. Rather, mothers make such decisions within socially negotiated accounts of what is morally adequate, and we go on to show how these decisions and the values informing them are socially patterned by class and ethnicity. Finally, we consider how both theory and policy can make a ‘rationality mistake’ in neglecting the importance of social ties and moral responsibilities in family life.