The tendency of members of many ethno-religious groups to marry within their group has been considered evidence for the persistent role of ascription in modern society. What is the role of the family of origin in this process? To answer this question, we study the marriage choices of Jews in the Netherlands, using a unique dataset and a novel analytical approach (i.e., multilevel analyses of sibling-data). Our models show that almost a third of the variation in Jewish endogamy can be attributed to a common family factor. Measured indicators of family background point to two underlying mechanisms: the intergenerational transmission of ethnic identities and the intergenerational provision of endogamous meeting and mating opportunities. Together, these mechanisms explain 75 percent of the total family influence. © The University of North Carolina Press.