This tale comes out of several attempts by yours truly to break the blank page syndrome that has rendered me unable to go on writting for too much time for my liking. Those attempts never went beyond my brain, but this one had better luck, so, here it goes.
1. Going towards the union of the kingdoms.
The lack of realiable chronicles relating the key events that would eventually lead to the creation of the United Kingdom of Spain surrounds with a midst of mistery the early stages of that process. The first of these key events takes place during the last years of Sancho III of Navarre (990-1045), when a succession of accidents remove his bastard son, Ramiro (d. 1026) and his youngers sons, Fernando (d. 1036) and Gonzalo (d. 1040) -1-. Thus, his elder son, García Sanchez, becomes king of not only Pamplona, but also earl of Castille and lord of Sobrarbe and Ribagorza. Eventually, through military coercion and with the support of Rome, García III of Navarre would marry Sancha of Leon, sister of king Bermudo III of Leon. A vain attempt, as Bermudo III would be succeeded by his son Alfonso (1036-1085) in 1067.
Perhaps García III of Navarre was a victim of his vindictive nephew Alfonso VI of Leon, who claimed in his chronicles that his uncle had murdered his royal brothers to avoid the division of the kingdom. To this day it has been pointed out that García was only 14 years old when his elder brother Ramiro died, but this author believes that García was up to the task and, even if the proves are scanty and most of the "history" related by Alfonso VI's chronicles are just rumours and slander, we cannot rule out the participation of García in those events. Perhaps he just took profit for the untimely dead of Ramiro, but there are serious doubts about the endings of Fernando and Gonzalo, as both died while hunting with their brother -2-.
However, all the efforts of Garcia to unify Hispania would come to naught when his only surviving son, Sancho IV, would die without a male heir in 1110 after the tragic hunting accident that killed his only son, García Sanchez. After that event, Sancho IV declared as his heir his cousin, Fernando García, son of the elder sister of his father, Urraca Garcés and García Ordoñez, earl of Najera. Less than twenty years later, in 1129, a son of Alfonso VI of Leon would inherit the throne of the unlucky Fernando I of Navarre, as we shall see.
-1- Here you have the POD: the division of the kingdom of Pamplona made by Sancho III in OTL does not take place.
-2- As we are going to see in this timeline, hunting can be quite damaging to your health if you have a bit of royal blood in your veins.