He is the founder and ecclesiastical patron of the perpetual chaplaincy established in the main chapel of the Monastery of San Francisco in Logroño.

[4] Their livestock, which included sheep, grazed in those lands, and hundreds of times they walked to the pastures of Extremadura or the royal valley of Alcudia, in La Mancha.

[6] Another Juan Martínez de Medrano died in the battle of Santarém on 17 July 1393, and was part of the retinue of King John I of Castile.

[8] His brother's namesake son Juan Martínez de Medrano served as the Official of the Knife or Carver (Trinchante) in the Household of Infante Henry in 1385, under the reign of King John I of Castile.

His role was part of the broader bureaucratic-administrative structure of the royal court, which included various high-ranking officials responsible for managing the prince’s household.

[2] Diego López de Medrano, Lord of Agoncillo, was a knight and royal ambassador at the service of King John I of Castile.

[12][17] According to a 16th-century document, the ecclesiastical patronage of the perpetual chaplaincy of Diego López de Medrano, Lord of Agoncillo during the late 14th and early 15th centuries, was established in the main chapel of the Monastery of San Francisco in Logroño.

[19] In approximately 1211, a captain of the Medrano family held the lordship of the castle and town of Agoncillo, situated near the city of Logroño, in the region of La Rioja.

[19] The Medrano family generously donated some land, including a tower, situated close to the Ebro River within the city of Logroño as a gift to Saint Francis, establishing the first Spanish convent of his Order there.

[20] As a result, the Medrano family are distinguished by their devotion to Saint Francis of Assisi and their generational patronage of the Franciscan order.

[21] Unfortunately, despite its centuries-long legacy of glory and sanctity, the convent met its demise in the 19th century due to the advent of liberalism and its accompanying laws.

[19] Ecclesiastical patronage, notably unknown to historiography, was one of the greatest demonstrations of supremacy and distinction that the nobility of the time could exercise.

This positioning allowed the Medrano family to control the passage of these rivers and oversee the important road running through the area.

The current town is believed to occupy the site of the ancient and now ruined settlement of Egón, from which it derives its modern diminutive name.

During the royal court's stay near the town, Alfonso XI of Castile bestowed Agoncillo, its fortress, and the castle between Arrúbal and Arroyuelo, along with their lands, rents, and judicial rights, upon his vassal and crossbowman Sancho Sánchez de Rojas and his wife Urraca Díaz on September 1, 1336.

Henry intervened in Castile and sought refuge in Rioja, while Charles II of Navarre took advantage of Peter I's weakening power to briefly seize Logroño and its territory.

[23] To repay the inhabitants of Viana for provisions taken while the royal court was stationed in front of Logroño, Charles II of Navarre ordered the sale of Agoncillo, its castle, and the village of Velilla, which had been recently regained, for three thousand florins, an agreement made in Pamplona on 15 September 1368.

However, following Henry II's victory in the province of La Rioja, the borders were restored to their original configuration, and the town of Agoncillo, along with its castle, was reclaimed by its rightful owner, Rodrigo Diaz de Medrano, in 1392.

[23] His daughter Dona Aldonza Diaz de Medrano inherited the Mayorazgo of Agoncillo, along with its stronghold, lands, vineyards, mills, and all associated rights and lordship.

This estate included Cidad de Porras with its stronghold, Virtus in Burgos, Spain with its castle, and Extramiana in Castile and León.

Pedro Gómez de Porras y Medrano, considering himself the legitimate successor, fulfilled tasks from his grandfather's will, including specific instructions for his burial in the Monastery of San Francisco in Logroño, with alabaster tombs and the placement of two Medrano family shields on the wall in the castle of Aguas Mansas.

Despite losing the succession case over Extramiana, Lope retained possession of Agoncillo, which remained in the Frías Salazar family until the abolition of the majorazgos in the early 19th century.

Diego's daughter Aldonza, who succeeded his son Juan de Medrano, became the Lady of Agoncillo and Velilla.

[23] Isabel's father Don Luis III de Beaumont was the son of Eleonore d'Aragon, the illegitimate daughter of king John II of Aragon and half sister of Queen Juana Enríquez.

Aldonza Diaz de Medrano is the ancestor of María Isabella Spínola y Spínola (1737–1801), who inherited the titles of XVI Countess of Siruela, VII Countess of Valverde, IV Marchioness of Santa Clara, VI Duchess of San Pietro in Galatina, and Princess of Molfetta.

She was the daughter of Francesco María Spinola, V Duke of San Pedro in Galatino and Mariana Francisca Spínola y Silva, VI Marchioness of Santacara, XV Countess of Siruela and Valverde.