Background: Men's age at first birth may negatively or positively affect alcohol-related morbidity and mortality, although little evidence is available. Methods: We used register data of over 22,000 brothers to analyze the associations between age at first birth and alcohol-related morbidity and mortality from the age of 35 until the age of 60 or 72. We employed conventional Cox models and inter-sibling models, which allowed adjustment for unobserved social and genetic characteristics shared by brothers. Results: The findings show that men's age at first birth was inversely associated with alcohol-related morbidity and mortality, independent of unobserved characteristics shared by brothers and of observed demographic confounders. Men who had their first child late at 35-45 years experienced lower alcohol-related morbidity and mortality (hazard ratio (HR) = 0.57, 95 % confidence interval (CI) = 0.43, 0.75) than men who had their first child at 25-29. Men who had their first child before age 20 had the highest morbidity and mortality among all fathers (HR = 1.36, 95 % CI = 1.09, 1.69), followed by men who had their child at 20-24 (HR = 1.12, 95 % CI = 1.00, 1.25). Conclusions: The results imply that the inverse association between men's age at first birth and alcohol-related morbidity and mortality is not driven by familial characteristics.