Between the end of the Middle Ages and the beginning of the Modern Age, the kingdoms of Castile and Aragon were ruled by the dynasty of Trastamara. Its historical origin is related to a bloody battle between the two half-brothers who fought for power in Castile, and its end is related to the arrival of Charles I to the throne of Spain, a monarch of the Trastamara lineage on his mother’s side (Joana the Loca), but who also descended from the House of Austria, as he was the grandson of Maximilian I of Hapsburg.
The fact that in the two main kingdoms of the Iberian Peninsula the same royal house governed was decisive for the formation of the so-called Hispanic monarchy .
The monarchs of the Trastamara dynasty in Castile
Between 1366 and 1369, in the Kingdom of Castile, there was a civil war between the supporters of two monarchs: Pedro I, the Cruel, and his half-brother, Enrique II, the Fratricide. The latter was the victor of the battle of Montiel in 1369 and with this episode began the dynasty of the Trastamara in the Castilian crown.
There were seven monarchs of this dynasty who ruled in Castile, more specifically five kings and two queens: Enrique II, John I, Enrique III, John II, Enrique IV, Isabel the Catholic and Joan the Mad. These seven sovereigns remained in power from the victory at the Battle of Montiel until the Austrian coming to power in the early 16th century (the first monarch of the new dynasty was Charles I).
Although the House of Trastamara is originally from Castile, it was finally consolidated in the Crown of Aragon
When in 1410 King Martin I of Aragon died without leaving any descendants, there was an unusual situation: there were six candidates for succession to the Aragonese crown. After a complex process of deliberations, those gathered in the Compromisso de Caspe, in 1412, proclaimed Fernando de Trastamara, Infant of Castile, as the new monarch of Aragon.
According to some chronicles and popular legends, the first of the Trastamaras obtained the Crown of Castile after murdering his half-brother, the legitimate heir to the crown. For this reason, Enrique II went down in history with a nickname , the Fatricide.
In addition to the Crown of Castile and Aragon, the House of Trastamaras also ruled the kingdoms of Naples and Navarre.
Some scholars have highlighted a particular aspect of this royal house: it is a dynasty of illegitimate origin, since it began with the coming to power of Enrique II (one of the bastard sons of Alfonso XI and who became monarch of Castile after kill his half-brother Pedro I with his own hands).