According to Islamic inheritance principles only the son of a deceased man can exclude his male agnates and preserve his estate within the nuclear family. In this study, I examine whether differences in son preference and fertility behavior between Muslims and non-Muslim households arise in an attempt to minimize the risk of inheritance expropriation by the extended family. I exploit cross-sectional and time variation in the application of the Islamic inheritance exclusion rule in Indonesia: between Muslim and non-Muslim populations affected by different legal systems, across men with different sibling sex composition, and before and after a change in Islamic law that allowed female children to exclude male relatives. I find that Muslim couples affected by the exclusion rule exhibit stronger son preference, practice sex-differential fertility stopping, attain a higher proportion of sons and have larger families than non-Muslims or Muslims for whom the exclusion rule does not bind.