Bonanno was born on January 18, 1905, in Castellammare del Golfo, Sicily, to Salvatore Bonanno and Catherine Bonventre. Joseph's uncles, Giuseppe Bonanno and his older brother and advisor, Stefano, led a mafia clan in Castellammare del Golfo. The clan's strongest ally was the leader of the Magaddino Mafia clan Stefano Magaddino, the brother of Joseph's maternal grandmother. During the 1900s, the clans feuded with Felice Buccellato, the boss of the Buccellato Mafia clan. After the murders of Stefano and Giuseppe, their younger brother, Salvatore, took revenge by killing members of the Buccellatos. In 1902, Magaddino arrived in New York and became a powerful member of the Castellammarese clan. When Joseph was three years old, his family moved to the United States and settled in Williamsburg, Brooklyn for about 10 years before returning to Italy. His father had returned to Sicily in 1911, and died of a heart attack in 1915. In 1921, Magaddino fled to Buffalo, New York to avoid murder charges.