Long story short it is a TL about a union between Portugal and Leon, there are multiple PODs the first is the birth of a son to João Anes de Lima, the second is the marriage of this character to Sancha Heiress of Leon if you want to know more about the PODs and the objective of the TL read this thread please: https://www.alternatehistory.com/forum/threads/hispania-iberia-united-by-portugal.398811/
I was working in the shadows for months in this TL, so I hope you enjoy.
Chapter I - Afonso IX, last king of Leon First years of life and coronation
Alfonso IX, born in 1171, son of Fernando II of León and Urraca of Portugal, reigned between the years 1188 and 1230, the year of his death. Alfonso was born of a marriage between cousins, common event in the Iberian monarchies of that time. For that reason, its position as successor of the king became uncertain after the marriage between its parents became null.
As soon as his father died his stepmother tried to put his own son on the throne, under the argument that her son was the deceased king's eldest legitimate son. Nevertheless, Urraca Lopes de Haro, widow of the king did not succeed in convincing the majority of the nobles and of the clergy and had the pretension of its son rejected by the royal curia. Urraca failed to unite the nobility in favor of his son, even her own family, the Haro, wasn't enthusiastic about the possibility of a child-king, in contrast, three important families stood out in defense of the rights of Infante Alfonso, the families Lara, Trava, and Lima.
Weddings: seeds of the crisis
Alfonso did not take long to fulfill his real obligations to generate an heir. Soon he married and during his lifetime he was married twice, but his lack of care in choosing his wives, although taking into account short-term diplomatic goals, led the peninsula to a crisis of succession that was the biggest one of Spain in that century.
In 1191 Alfonso married his first wife, Teresa, daughter of the king of Portugal, Sancho I, who was also his cousin. This marriage was considered null in 1194 and generated three children, Sancha, Fernando, and Dulce. Sancha and Fernando remained in Leon, but Dulce was taken to Portugal with his mother. Many years later Sancha married Rodrigo Anes de Lima in 1211.
In 1194 Alfonso married again with another cousin, Berengaria of Castille, this marriage generated two sons and two daughters and was also annulled.
With the annulment of the second marriage of Alfonso, a crisis seemed to have been avoided, since now Berengaria could not discredit the legitimacy of the first-born of Alfonso without discrediting its own son.
In 1206 the king made a clear definition that Fernando would be its successor and in the case of its death, the masculine children of Berengaria would inherit, later the women daughters of Teresa and finally the women of Berengaria.
Diplomacy
In 1194 the Cardinal and Papal Legate, Gregory, was sent to Spain to arbitrate the differences between the Christian kingdoms. In the same year, the agreement of Tordehumos was reached, with such agreement several castles in litigation are exchanged and the borders were defined again.
Despite the agreement Alfonso always maintained distrusts against Castile, seeking to secure its border with Portugal and the friendship of Navarre and Aragon. The Almohad power also always kept Alfonso from trying to expand southwards, on the contrary, he sought help from the Muslims to attack Castile and Portugal, when those kingdoms entered into an alliance around the turn of the century. In these wars all kingdoms had losses, but Leon had the greatest, losing not only men and wealth but the support of the other kingdoms and extensive strips of territory.
This situation changed in 1212 when it happened the battle of Navas de Tolosa. This battle that definitively destroyed Muslim cohesion did not have a Leonese participation, but it profoundly affected Leon's diplomacy, which began to seek expansion southwards, mainly to reach the city of Seville and to conquer as much of Andalusia as possible before the neighboring kingdoms. The king then spent almost the whole of its last two decades of his life devoted to the reconquest, expanding the territory to the south of Leon.
Deaths and successions
In the year 1211 the heir to the throne of the Kingdom of Castile, Ferdinand, died at the age of 22 passing away with no offspring. The new heir was Henry, the second son of Alfonso VIII of Castile. In turn, in 1214 the king of Castile also died leaving his son, Henry I, a boy of only ten years of age as sovereign. The former wife of the king of Leon, Berengaria, was then made his protector.
On that same year in the kingdom of Leon, the heir of Alfonso IX died, Ferdinando was the heir of Leon and son of the king with his first wife, he was only 22 years old. With his death, the throne of Leon happened to be now part of the inheritance of the children of Berengaria and Alfonso because next in the line of succession was another Ferdinando, half-brother of the recently deceased infante.
In 1215 Dulce, daughter of the king of Leon was engaged to Henry I of Castile. The engagement was supposed to become a marriage between 1219 and 1221.
Henry was a young king and so was not fit to rule, at age 13 in 1217 he was still interested in playing games and living his life of young teen until in a summer day he played with other children a little game of polka dots in the shade of a house when a tile slipped and hit the top of his head, causing a sinking of the skull. His death remained a secret for some time and was only revealed after the coronation of Berengaria.
The fact that the king was under the protection of Berengaria in Palencia and that she was his successor led to the beginning of a small scandal when the death was revealed, but the supporters of the new queen soon drowned out these rumors.
Immediately after knowing about the death, Alfonso IX declared that he was Henry's heir, as the closest living relative of the late king by male line. However, it was too late, and indeed his eldest son had left Leon in the days before at the request of Berengaria, with the consent of Alfonso, not knowing yet that Ferdinand would be crowned king of Castile.
Alfonso felt betrayed and ordered his son to return, his son and the mother of his son sent to him a message saying that the king of Leon could not give orders to the king of Castile. Alfonso immediately went on to coordinate a conspiracy with the noble Castilian Alvaro Nunez de Lara, but his conspiracy was discovered and Lara was executed for treason. By that moment, Alfonso and Ferdinando started to exchange increasingly harsh correspondences.
According to the chronicles of the kingdom of Leon, Alfonso wanted to wage war against the kingdom of Castile, but it was the contrary advice of João Fernandes de Lima and the appeals of his daughter Sancha and the Archbishop of Santiago that prevented Alfonso from summoning his army against Castile.
Political strategy of Alfonso IX, the “Party of Sancha”
After the betrayal of his children, Alfonso decided to block the succession of his surviving sons and made Sancha his successor. In 1218 the king, together with his main advisors and friends, created a strategy to secure the power of Sancha's supporters.
The main piece in this political game was Joao Fernandes de Lima, chosen to be the Mordomo (Steward of the Kingdom) between 1220 and 1224, “Alferez” of the Kingdom between 1224 and 1228 and again Mordomo in 1228. In this position of power, Joao could distribute tenancies to the allies of Lima, like Rodrigo Fernandez, Alferez of the king after 1228, Diego Froilaz, son of the count Froilaz Ramirez and stepfather of some illegitimate children of Alfonso IX, and several nobles of the families that usually supported Alfonso, mainly the Trava, the Lara and obviously the Lima . Besides the nobles, Alfonso had the support of Bernardo II, archbishop of Santiago and by consequence of the greater part of the Leonese clergy.
In addition to creating and cementing the power of what was known as the Sanchist Party, the partisans of the infanta sought the support of the other kingdoms, seeking to isolate the kingdom of Castile diplomatically. Many Leonese nobles had family and political relations with Portugal and this was the first kingdom courted by Alfonso and Joao. In the year 1219, an alliance with Portugal was reached, as well as a marriage agreement between Alfonso's granddaughter and the son of Alfonso II of Portugal, not Sancho, heir to the throne, but his brother Afonso. The following year Alfonso was able to marry his second daughter, Dulce, with the heir to the throne of Navarre, Pedro, future Pedro II. With this movement, Alfonso diplomatically advanced the siege of Castile. In 1228 Sancha was quick to negotiate with Louis VIII of France a marriage for her son Tiago (translated as James), heir to the throne of Leon, with Isabel of France, born only three years before, the marriage was to be consummated after 1238.
The king's machinations were ended in 1230 unexpectedly, he wished to leave Sancha in a good position to make a peaceful transition, but his early death without the full consolidation of the sanchist power and the sheer Leonese bad luck of Ferdinando being already mobilized for war at that time were the main reasons for the start of the Leonese War of Succession.
Map of Spain at the death of Alfonso IX
Notes:
1 - North Extremadura: Region between the Sierra Central and Tagus River
2 - South Extremadura: almost entirely conquered in the reign of Alfonso IX from 1210 to 1230.