Molina was born at Guaraculén, a big farm located near Villa Alegre (General Captaincy of Chile), where he lived until he was 5 years old. In the current province of Linares, in the Maule Region of Chile. His parents were Agustín Molina and Francisca González Bruna. From an early age he was attracted to the nature of the environment where he was, as well as to his study, he especially enjoyed studying nature on his family's farm, which he visited periodically, alternating with his studies. This is how Molina described his interest in nature: