[1] While Aux the Younger was educated, his father was recruited by Francisco de Garay to return to Catalina's lands and establish an official settlement, later renamed Santo Domingo, current capital of the Dominican Republic.

Aux the Elder and Garay became immensely wealthy thanks to their newfound gold mines, leading the former to be appointed alcaide and alguacil mayor of the Fuerte de Santo Domingo.

In 1521, two years after his father's death, he was sent by Garay to the continent at the head of a rescue fleet to find Alonso Álvarez de Pineda, who had gone missing in his own expedition in the Pánuco River.

Aux failed to find Pineda, who had been killed by Huastecs, and after skirmishes with those, he eventually desisted and headed to Veracruz to reinforce the expedition of Hernán Cortés, who was at the time preparing the siege of Tenochtitlan.

[4] Aux commanded one of the Spanish brigantines during the siege of Tenochtitlan,[5] the first showing in a career as a land conquistador in which, according to comrade and chronicler Bernal Díaz del Castillo, he served excellently in a long list of conquests.