This paper studies intergenerational living arrangements in the presence of pre-school children. Two particular driving forces behind living arrangements are considered: intergenerational labor specialization in childcare and work on the job; and sharing the companionship of children as a household public good. The theoretical model yields implications for intergenerational co-residence, maternal labor supply, and investment in children. Using China Health and Nutrition Survey data, we find that women are more likely to co-reside with their mothers-in-law if they have higher earning abilities, or if they have fi rstborn sons, who are considered more valuable household public goods under the widespread son preference in China. We also fi nd that among extended households with higher probability to co-reside, the mothers are likely to spend more time on the job and be less involved in family chores, and the male children, on average, receive better health insurance and medical services than the female children do.