In the Industrialized West, ageing populations and cultural diversity-combined with rising property prices and extensive years spent in education-have been recognized as diverse factors driving increases in extended family living. At the same time, there is growing awareness that household size is inversely related to per capita resource consumption patterns, and that urgent problems of environmental sustainability are negotiated, on a day-to-day basis (and often unconsciously), at the household level. This paper explores the sustainability implications of everyday decisions to fashion, consume, and share resources around the home, through the lens of extended family households. Through interviews with extended family households in Australia, we explore the potential for these living arrangements to reduce resource use, and thus improve sustainability outcomes. In these households, a desire to care for and support family members in hard times (rather than an overt sustainability agenda) has promoted particular modes of extended family living, including unique forms of sharing and pooling material goods. But cultural values of privacy, space, and independence-and the sanctity of the nuclear family-have led to duplication (and even multiplication) of household spaces, appliances, and resources, under one roof. The potential environmental and economic benefits of resource sharing within larger households are thus mediated by deep cultural values and exigencies of everyday life.