A family reconstitution study of the Krummhörn population (Ostfriesland, Germany, 1720–1874) reveals that infant mortality and children’s probabilities of marrying or emigrating unmarried are affected by the number of living same-sexed sibs in farmers’ families but not in the families of landless laborers. We interpret these results in terms of a “local resource competition” model in which resource-holding families are obliged to manipulate the reproductive future of their offspring. In contrast, families that lack resources have no need to manipulate their (...) offspring and are more likely to benefit from allowing their offspring to capitalize on whatever opportunities to reproduce present themselves. (shrink)