Women are generally underrepresented in politics. Some explanations to this phenomenon emphasize cultural legacies; others focus on political and labor market institutions to explain. We investigate the joint effect of culture and institutions on the political representation of women. To gain leverage on cultural traits, we focus on two prototypical historical family types: nuclear vs. stem families. In nuclear families, newly-weds started new households and women stayed at home, while in stem families the newly-weds stayed with in-laws, grandmothers did more housework and young females were more likely to be in paid work. As a result of female participation in the market economy, women in stem families gained bargaining power vis-à-vis men relative to women in nuclear families. Our hypothesis is that in-household gender equality shapes attitudes about women’s active participation in politics. To estimate the causal effect of family types on female political representation, we apply an instrumental-variable strategy based on medieval inheritance laws, using historical and contemporary data for Spain. Our preliminary findings show that regions with a tradition of stem families elect more female councilors in local elections than areas where nuclear families dominated. Then, we assess the role of cultural norms, labor market institutions and political institutions (in particular, the adoption of gender quotas in party lists) in the evolution of the gender gap between regions with different historical family types during the democratic period (1977-2015). To conclude, we discuss the implications of our findings for theories of cultural persistence and change.