Genetic genealogy is a rapidly growing field. The potential for genetics to make genealogical connections and break brick walls is starting to be untapped. This is more so for Latin American and Caribbean societies where limited or non-existent documentation is a reality. This article uses advanced genetic testing to draw genealogies for a particular set of Puerto Rican families, the Sotomayor and Colón families, with connections to the Iberian Pereira lineage. In the critical analysis of the existing fragmented and isolated documentation with advanced genetic testing, mainly Y-DNA, and in its proper historical context, long-standing brick walls have been broken. The study also illustrates, through the prism of genetics, the complex anthroponymy system of Iberian surnames in the American context, which gave a legitimate and significant role to maternal ancestry. As one of the very few instances of a Y-DNA genetic match between two men of different surnames at the edge of genealogical time frames, this study offers insights into the larger use of genetics for genealogy and anthroponymy.Popular lore and long-standing legend say that the Sotomayor family from Puerto Rico's north-west descend from Galician noble Don Cristóbal de Sotomayor, who settled in the island in 1509 and died during the indigenous rebellion in 1511 shortly after establishing the Villa de Sotomayor. 5 The present study refutes this legend, at least with regard to the direct male descendants of Juan de Sotomayor, who was born in Aguada c.1740. In doing so, a new genealogy is offered, supported by -and actually only possible with -genetic data, particularly Y-DNA. Similarly, there has been research done on several branches of the Colón family, some of which can be traced to the sixteenth century, allegedly related to the family of Admiral Don Cristóbal Colón (Christopher Columbus). 6 But the branch participating in the present study had not been able to go beyond the early nineteenth century. Of particular interest is the fact that the genetic matching of these two families places their ancestor in common some 500 years ago, beyond the genealogical time frame, which for Iberian-American societies could be between 300 and 500 years before the present. The genealogical journey between these families also allows us to observe the intricate and complex anthroponymy system of Iberian-American surnames that incorporates maternal surnames in legitimate offspring.