During the reigns of Fernando II and Alfonso IX, the kingdom of León became home to several Portuguese aristocrats. Their relations with the Galician and Leonese nobility helped them create many cross-border ties and a powerful network of family-based relationships, which heavily influenced the course of the main political conflicts of this period. In this article, the authors try to situate these migrations in their context, analyzing their cycles, causes and favorable conditions, describing each of these exiles and assessing their influence on both Portuguese and Leonese politics.