This paper examines the socio-demographic characteristics of newly enfranchised groups, focusing on women. Previous research has addressed this topic using aggregated data, risking ecological fallacies when inferring individual behaviour. I overcome this limitation by analysing newly available, fine-grained historical electoral data on individual socio-demographic characteristics. The dataset covers voters during the Second Spanish Republic (1931–1939), the first time women were granted the right to vote in Spain and includes electoral results at the district level. My research expands on the literature on the turnout gender gap by identifying which groups of women, if any, tended to vote at lower rates than men. It also investigates the role of family dynamics, such as sibling relationships, in shaping voting behaviour. Specifically, it examines whether the presence of female family members influenced individuals’ likelihood of voting in subsequent elections. The findings reveal a positive influence of older sisters on younger sisters’ likelihood of voting in elections where they became eligible to vote by age— a pattern not observed among brothers. Finally, the level of disaggregation of the electoral results enables an analysis of women’s ideological preferences by examining population composition by sex and accounting for other socio-demographic characteristics. By addressing limitations in prior research and leveraging detailed historical data, this study sheds light on how women’s participation and preferences were expressed in early elections following enfranchisement. It offers valuable insights into the interplay between gender, family structures, and political behaviour during a transformative period in electoral history.