Alonso was the son of a prosperous merchant, Diego de Curiel, who maintained important relations with the Court of Madrid.
In August 1577, Jerónimo commended his nephew Alonso de Curiel to the care of the governor of the Habsburg Netherlands, John of Austria.
On 9 March 1578, Don John ordered Curiel to participate in an important financial negotiation on behalf of Philip II of Spain to obtain funds from Antwerp, Madrid and Burgos.
[1] It has been suggested that Dutch and Belgian historiography underestimates Curiel's role in bringing about the reconciliation of the Walloon provinces to the royal cause in the 1579 Treaty of Arras.
[1][2] On 4 August 1603, Philip III appointed him as Agent of the Spanish Crown for trade with "the States of Flanders, Islands of Holland, and Zealand, vassals of Princes and Republics, friends and Neutrals.