Although the Catholic Monarchs in 1492 were the ones who, after taking Granada, finished the "Reconquest" and unified the Christian kingdoms, they were not the first to try. Many had the idea, but only the attempt of Urraca I of Castilla y León and Alfonso I of Aragon and Navarre "the Battler » is noteworthy.
Alfonso I and Magpie
After the death of Alfonso VI of Castilla y León without male offspring, we ignore the death of his son Sancho in the battle of Uclés as a result of his passionate love with the "Moorish" Zaida, Princess Urraca obtained the throne from her father (being the first time a woman inherited the throne). The nobles of both kingdoms, Castilla-León and Aragón, saw the opportunity to unite both kingdoms with the marriage of Urraca, widow of Raymond of Burgundy, and Alfonso. They got married in 1109, but their disparate characters quickly gave rise to fights, insults and even Alfonso came to lock up Urraca. In the end Alfonso repudiated his wife and the Pope was also very happy, given their consanguinity (they were cousins). And here the first unification attempt ended.