By means of a large-scale quantitative approach, this study examines the declared family language practices of Swedish-English bilingual families living in Sweden, and how an array of family-external and family-internal social factors correlate with divergences in these practices. For the purpose of this study, a Swedish-English bilingual family consists of two parents, one of which is an L1 English speaker, and the other is an L1 Swedish speaker, as well as their children. The data comes from a digital questionnaire completed by 438 families, which was analysed using non-parametric statistics. The results show that despite a preference for English amongst the parents in these families, their children are more likely to use Swedish in sibling interaction, which can be regarded as an indication of the influence of wider society on home language practices. The results also show that a number of social factors correlated with a divergence in declared language practices in these families, namely, parental occupation, the migratory history of the family, parent’s marital status, family involvement in parent-child English speaking groups, and whether the mother or the father was the L1 English speaker. Other typically cited social factors, such as parental education level, showed no significant correlation with declared language practices in these families. The study comments on raising bilingual children in a context where both languages are valued in society, and the implications for this internationally. The study also exemplifies the complex, context sensitive situation that is encountered when attempting to fully understand family language policies more generally.