He inherited this position through his maternal lineage, tracing back to his grandfather Garcí Bravo de Lagunas, who established a military testament in his favor.

He became the ecclesiastical patron of the main chapel in the Franciscan monastery of Atienza, reconstructed by his sister Catalina de Medrano, which also served as the family mausoleum.

After settling in Atienza, Magdalena and Diego had at least four more children, including Garcí Bravo's sister Luisa de Medrano.

[6] After her father's death, his mother Magdalena was received as a lady of Queen Isabella I of Castile's court, alongside her daughter, Catalina de Medrano, who frequently appeared in the retinue of King Ferdinand II of Aragon.

[7] Educated at the University of Salamanca in Civil and Canon Law, the Medrano family prepared for roles as corregidores, judges, and advisors to the Crown's Councils.

Originating from Soria and Viana and linked to the castles of San Gregorio and Barajas (Madrid), they initially settled in Ciudad Real.

In the Castilian War of Succession, Diego's maternal grandfather Garcí Bravo de Lagunas, alcaide of Atienza, secured the city of Sigüenza for Queen Isabella I of Castile.

[10] His maternal grandfather Garcí Bravo de Lagunas made a military testament in the royal style, which was later legally recorded on 31 May 1570, by Juan Sánchez Canales, a notary in Toledo.

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

[13] The House of Medrano's patronage of the Franciscan Order began in 1211 when Saint Francis of Assisi visited their castle of Aguas Mansas in Agoncillo.

That same year, Garcí's relatives, the lords of Agoncillo, donated land and a tower in Logroño to Saint Francis, enabling him to establish Spain’s first Franciscan convent.

Her death at age 13 without heirs triggered a new legal dispute over the Marquessate of Lanzarote, which was ultimately ruled in favor of the descendants of Garcí's second son, Baltasar de Medrano.

[12] Martín Pedro González Medrano de Castejón Belvís e Ibáñez obtained the Marquessate of Lanzarote through a ruling of the Council of Castile on 14 March 1729.

The decision, based on the Laws of Toro, granted him possession of these mayorazgos, along with all associated properties, revenues, and rents accrued since the death of Leonor Duque de Estrada, up until their formal transfer and restitution.

[22] Garcí's siblings are recorded in his mother Magdalena's will, dictated in Atienza on December 1, 1527, and preserved in the Archive of the Dukes of Villahermosa.

[27][28] On 1 September 1552, Charles V, Holy Roman Emperor, issued the Carta Ejecutoria de Hidalguía, confirming the noble status of the ancient Medrano family.

[29] Compiled in Valladolid and Arenas, Spain, it includes genealogical records, official signatures and seals, and copies of rulings from Countess Juana Pimentel, King Henry III, and Álvaro de Luna.

Written in Gothic script on 20 parchment sheets, the document features the Holy Roman Emperor's coat of arms with gold floral decorations.