This paper examines the influence of parental preferences for grandchildren on young adults' entry into cohabitation and marriage. We also consider the influence of young adults' own fertility preferences on their cohabitation and marriage behaviour. We develop a theoretical framework explaining why these childbearing attitudes influence young people's cohabitation and marriage behaviour. The results show that the childbearing preferences of young women and their mothers affect their choice between cohabitation and marriage, so that wanting many children increases the likelihood of choosing marriage. Young men whose mothers want them to have many children enter any type of co-residential union, either marriage or cohabitation, at a much higher rate than men whose mothers want them to have fewer children. Our results also provide insights into the childbearing behaviour of cohabitating couples.