The Male Sibling Effect: Understanding Son Preference Among Nigerian Women

This study examines whether the number of brothers a woman grows up with is associated with her ideal number of sons among Nigerian women. Using women's data from the 2018 Nigeria Demographic and Health Survey (n = 40,628), I estimated a weighted negative binomial regression model predicting ideal number of sons. The findings show a positive and statistically significant association between the number of brothers and ideal number of sons. Women who grew up with more brothers are more likely to express desire for a higher ideal number of sons, even after controlling for sociodemographic and economic factors. Additional robustness checks showed that the association remained after controlling for total sibship size, number of sisters, and ideal number of daughters. Interaction models further showed that the association varies by age-cohort and education, but not by region of residence. The association is strongest among younger women and is slightly stronger among women with higher levels of education. These results suggest that early sibling environments may play a role in shaping women's fertility preferences and son preference in Nigeria.