Luis de Aliaga Martínez was born in Mosqueruela in 1560, the son of a nobleman who nevertheless ran a cloth business.
On 6 December 1608 he was named confessor of Francisco Gómez de Sandoval, 1st Duke of Lerma, favourite of Philip III of Spain.
Lerma soon had Aliaga appointed confessor to the king (a position that had previously been held by Diego Mardones, a member of the Franciscan Order, who became Bishop of Córdoba).
Aliaga accepted the king's offer to name him Archimandrite of Sicily and a member of the Spanish Council of State.
The new favourite, Cristóbal de Sandoval, Duke of Uceda had Aliaga named Grand Inquisitor of Spain in 1619.