Objective: We investigate the association between the geographic proximity of the grandparents on net marital fertility and maternal survival in Sweden, 1900Sweden, -1910 the framework of the cooperative-breeding-hypothesis. Methods: Data were derived from Swedish full-count censuses and the Swedish Death Index. Married couples were linked to their parental households. Poisson and logistic regression analyses were used to investigate the association between the geographical proximity of the grandparents on net marital fertility, which we measured as the number of surviving children born between 1900 and 1910, and the mother's survival. Models were fitted with and without fixed effects to assess the effects of unobserved characteristics shared at the parish and the family level.