His descendants accumulated possessions and titles that increased the power of the lineage, which received the definitive backing in 1445 with the concession of the Dukedom of Medina Sidonia, which in 1520 was granted the original Grandee of Spain.

At the end of 1281 or beginning of 1282, he intervened in the pact between the aforementioned Yusuf and Alfonso X, by virtue of which the Merinid sultan would help the Castilian monarch against the rebellious infante Don Sancho.

Later, in 1294, Sancho IV himself resorted to Guzman for the defense of Tarifa, a place threatened by the prince Don Juan, uncle of the monarch, with the help of the Merinids and Nasrids.

[2][3] In 1369, King Henry II of Castile granted Juan Alfonso Perez de Guzman, 4th Lord of Sanlucar, the County of Niebla for his loyalty in the First Castilian Civil War that he had maintained with his half-brother Peter I the Cruel.

The Condado takes its name from the Huelva town of Niebla, and included the town of Niebla and its villages, namely: Trigueros and Beas, Rociana, Villarrasa, Lucena, Bonares, Calañas, Facanías (today Valverde del Camino), the farmstead of Juan Pérez (today in La Puebla de Guzmán), Paymogo and El Portechuelo, Peña Alhaje and the Campo de Andévalo.

All this gave the house a new great impulse, to which was added the institution of a Majorat on the part of the Count in 1371, with the real estate and jurisdictional goods that he had inherited together with those contributed in dowry by his wife.

Likewise, during the crisis that John II had with the Infantes of Aragon, between 1441 and 1444, the 3rd Count supported the monarch so that the kingdom of Seville remained mostly in his favor, a service for which he was rewarded in 1445 with the concession of the Duke of Medina Sidonia.

The granting of this title meant that the dignity of Count of Niebla was associated with the Duke's first-born son, destined to succeed him as head of the house, in a sort of internal "principality".

In 1457, the 1st Duke, married to María de la Cerda, of the House of Medinaceli, established a entailed estate, with the King's permission, in favor of his bastard son Enrique, since he had no legitimate descendants with his wife.

The first one was maintained with the House of Medinaceli that demanded the return of the villa of Huelva, since Maria de la Cerda had contributed it to the marriage in dowry, but had died without having had children with the Duke.

The instability caused by the civil war between Henry IV of Castile and his half brother Alfonso, was used by the house to expand its domains by annexing Gibraltar and Jimena.

The attractiveness of Gibraltar resided, among many other aspects, in the fact that it was endowed with an annual royal revenue of approximately 1,500,000 maravedíes, for the military expenses of the commandery, provisioning and garrison, which would last until the definitive conquest of the Kingdom of Granada.

On the other hand, Jimena, which had been conquered from the Nasrids of Granada in 1456, was taken from the Duke of Alburquerque in 1468, which generated a long lawsuit that concluded at the beginning of the 16th century, with the house paying 6,000,000 maravedís as compensation for the town.

At the end of 1494 or beginning of 1495, the 3rd Duke lent his support to the Adelantado Alonso Fernández de Lugo, who definitively conquered Tenerife, which brought the house sugar mills and real estate in the Canary Islands.

In 1503 a new entailed estate of the house was approved and included Huelva, Jimena, San Juan del Puerto, the dozavo de Palos, Olivares and Villafranca.

In 1505 the 3rd Duke Juan threw himself to offer his support to Joanna and Philip, in front of the "threat" of the queen's father Ferdinand the Catholic, by means of an embassy that left Sanlúcar to Flanders.

In response, they named him " Royal Lieutenant and Captain General of the kingdoms of Granada, Cordoba, Jaén, the Algarves, Algeciras, with all Andalusia" and, according to a document, "and of Murcia"; position that never came to be exercised.

From then on the house went through a series of vicissitudes caused fundamentally by the contracted family alliances, the territorial lawsuits pending resolution and the political instability that the Andalusian nobility was going through before the return of the Catholic King.

The Aragonese monarch intended to marry his granddaughter Ana of Aragon, daughter of Alfonso, extramarital son of King Ferdinand and Archbishop of Zaragoza, to Duke Enrique.

The king, from Seville, asked Pedro Girón for the fortresses of Sanlúcar, Vejer and Huelva, who replied that he should deal directly with the duke, who was already married and lord of his estates.

Niebla, by orders given by Girón before leaving for exile, resisted the king, so the town suffered the assault of the royal troops in November 1508, which caused a popular massacre remembered for its crudeness.

On their return they accepted the king at court and established their residence in Osuna, where the duke died in January 1513, childless and leaving his sister Mencía de Guzmán (at that time Pedro Girón's wife) as his universal heir.

As a consequence, the 9th Duke lost the Lordship of Sanlúcar in 1645, was banished and the Capitanía General de la Mar Océana Sea passed to the House of Medinaceli.

It cultivated in its lands of the Aljarafe, of the Lower Guadalquivir, of the Campiña de Jerez and of the alfoz of Medina Sidonia, the Mediterranean triad (wheat, olive tree and vineyard) and the horticultural crops.