An isonymic analysis has been carried out using a sample of 1529 reconstituted families residing during 1870–1964 in Aranjuez, an urban area situated south of Madrid, Spain. The random, non-random and total-components inbreeding coefficients from isonymy were obtained and the various combinations of surnames compared in order to infer the patri- or matrilocal pattern of residence. Throughout the period studied the random component of inbreeding (Fr) has not changed, in contrast to the non-random component (Fn), thus suggesting the latter could be responsible for the reduction of total inbreeding. Using several methodological approaches (biplot analysis, α, ν and percentage of immigrants) the predominance of the immigration of grooms was interpreted in terms of Aranjuez as a matrilocal pattern of residence. From this study it can also be concluded that surnames provided by reconstituted families are good estimators of inbreeding and migration.