Turi's right: the American Mafia Donship definitely has not been an hereditary office. Other than the two examples he cited, there have been only two more that I know of: Joe Bonanno's attempt to make his son Salvatore (Bill) the Don, which failed; and Joe Magliocco taking over from his brother-in-law, Joe Profaci, which precipitated the war that lead to the Bonanno failure. It's been a question of might makes right, more often than not involving treachery. That's what makes "Sopranos" a here-and-now show: Everyone wears a wire, nobody has any loyalty, and even the Don's fallable.