This paper examines how culture impacts within-couple gender inequality. Exploiting the setting of Germany's division and reunification, I compare child penalties of East Germans who were socialised in a more gender egalitarian culture to West Germans socialised in a gender-traditional culture. Using a household panel, I show that the long-run child penalty on the female income share is 23.9 percentage points for West German couples, compared to 12.9 for East German couples. The arrival of children also leads to a greater increase in the female share of housework and child care for West Germans. I add to the main findings by using time-use diary data from the German Democratic Republic (GDR) and reunified Germany, which provides a rare insight into gender inequality in the GDR and allows me to compare the effect of having children in the GDR to the effects in East and West Germany after reunification. Lastly, I show that attitudes towards maternal employment are more egalitarian among East Germans, but that the arrival of children leads to more traditional attitudes for both East and West Germans. The findings confirm that socialisation has a strong impact on child penalties and that family policies may have an impact on gender inequality through social learning in the long run.