Raised in Hell's Kitchen, Genco worked at his father's grocery store from an early age. He became firm friends with the hired hand, one Vito Corleone and was upset when Vito was moved out but the neighbourhood Don, Massimo Fanucci, even offering to steal from his father to help his jobless friend. Vito refused, saying this would be an offense to his father.
When Vito became the new Don of the neighbourhood, he hired Genco to act as his consigliere, and named his front company 'Genco Pura' after his friend. Genco served him loyally, showing incredibly insight, especially when Vito's son Santino wanted to join the Family business, the wily consigliere had the youth closely assigned to his father as a bodyguard so he could closely learn the Family business, as well as be kept under Vito's control.
Genco remained an intelligent and active advisor until he was stricken with cancer and died with the Don at his side in 1945.
Genco was succeeded as consigliere by Tom Hagen, Vito's adopted son, whose appointment was contraversial due to his German-Irish heritage. Many, including Corleone foe Virgil Sollozzo, and occassioanlly even Sonny Corleone himself, claimed that Genco, as a Sicilian, was more adept as a 'wartime consigliere'.