The Godfather Wiki

Santino "Sonny" Corleone was Don Vito's first child and underboss of the Corleone clan.

The underboss or street boss (also known as sotto capo or capo bastone) is the second most important position in a crime family, directly beneath the Don himself. The underboss is usually appointed by the boss himself. The underboss is in charge of all of the capos and is usually first in line to become acting boss if the boss is imprisoned or otherwise incapacitated, while also frequently seen as a logical successor.

Notable underbosses

Tramonti family