Juan Alonso de Guzmán was the son of Enrique de Guzmán, 2nd Count of Niebla, 5th Lord of Sanlúcar, and of Teresa Suárez de Figueroa y Orozco, Lady of Escamilla and Santa Olalla.
He managed to keep control over the area of Seville, and to launch a counterattack that allowed the recovery of the enemy bases of Jerez, Acalá de Guadaira, Carmona and Córdoba.
For this, he was awarded the title of Duke of Medina Sidonia by King John II of Castile on 17 February 1445 [1].
In 1462, he played the leading role in the Reconquest of Gibraltar, which had been lost in 1411, and where his father had died in the failed diege of 1436.
Juan de Guzmán, 1st Duke of Medina Sidonia, died in December 1468 and was buried in the monastery of San Isidoro del Campo in Santiponce.