Franzese was born on May 27, 1951, in the Brooklyn borough of New York City, to John "Sonny" Franzese, a Colombo crime family underboss, and Cristina Capobianco-Franzese, although Michael had initially questioned his actual biological father. Franzese had initially believed that he had been adopted by John after his mother divorced Frank Grillo, who Franzese thought to be his biological father. Michael says he had gone by the name "Michael Grillo" until he was 18 years old. However, it was later discovered that John, already married with three children, had gotten the 16-year-old Capobianco, a cigarette girl at the Stork Club in Manhattan, pregnant with Michael, so Capobianco married Grillo to avoid having a scandal surrounding having a child out of wedlock. After the mob allowed John to divorce his first wife, Grillo disappeared, and he married Capobianco.