In 1901, Don Ciccio ordered the death of Vito Corleone's father, Antonio, because he did not step down to him, and also ordered the death of Vito's older brother Paolo for swearing to avenge his father's murder. Vito and his mother Signora Andolini went to visit Don Ciccio so Vito could be safe, the Don refused, and Mrs. Andolini held a knife to the Don's throat in order for Vito to escape. Vito was then aided by relatives to get out of Sicily, and Vito traveled to New York and was accidentally renamed Vito Corleone. Several years later, as an adult, Vito returned to Sicily and exacted revenge on Don Ciccio and his enforcers, Strollo and Mosca. Tommasino, a loyal ally of Vito Corleone, became the new mafia chieftain of Corleone.
In 1946, after Vito's youngest son Michael murders drug lord Sollozzo and Captain McCluskey, Michael was immediately dispatched to Sicily to hide from the Tattaglia family and the New York Police, and was placed under Tommasino's care.
In the late 1940s the clan was involved in a turf war over Corleone with Guido Quintana of Montelepre, after the latter was forced out of that town by the forces of Salvatore Giuliano. Quintana succeeded in taking over Corleone, but his succcess was short-lived as he was later killed by Salvatore Giuliano.
A few decades later, in 1980, Don Tommasino was killed by an assassin called Mosca of Montelepre, and after his loyal underling Calò was killed trying to avenge his murder, the Tommasino clan may have disolved.
Don Ciccio's Clan structure (1890s-1922)
Tommasino Clan structure (1922-1980)