Second sovereign of Castile (1035-1065) and Leon and Galicia (1038-1065) born in Castile, congominate the Great or the Magnus, whose reign represented a milestone on the long road to the unification of the peninsula's Christian kingdoms Iberian. Second son of Sancho III of Navarre or Sancho Ide Castile, and of the Infanta Mayor of Castile, he inherited the kingdom of Castile from his father, whose territory was partly included in Navarre. He married Princess Sancha, sister of Bermudo III de Leon, who upon his death (1037), also occupied the throne of Leon and was crowned its sovereign (1039), including from Galicia.
He reorganized the administration of his kingdom and reduced the hereditary powers of the nobles. With the death of his brother García IV of Navarre, killed (1054) by Fernando's troops in Atapuerca, he annexed Navarre. He then regained Viseu and Coimbra in Portugal and San Esteban de Gormaz and Berlanga in eastern Spain, domains of the Moors. Then the kingdom of Toledo (1062), and was recognized as sovereign of the Moorish kingdoms of Zaragoza and Seville. Before he died in Leo, contradictorily in his struggle for unification, he divided the empire among his sons. Thus, his eldest son Sancho II of Castile, his main kingdom, Alfonso VI took over the domains of Leon, and García with Galicia. To his daughters Elvira and Urraca he left ownership of two monasteries.
Source: http://www.dec.ufcg.edu.br/biografias/
Order F - Biography - Brazil School
Source: Brazil School - https://brasilescola.uol.com.br/biografia/fernando-i-de-castela.htm