Sometimes when family is involved, and something happens, deep down you "know" for sure. If your father is accused or suspected of doing something like that, and you grow up knowing that he was responsible for murders and killings, and then an uncle who was accused of betraying your father is first mistreated by your father and then suddenly dies while in the company of your father's most trusted associate, you grow up "knowing" what really happened.
Remember, even his daughter Mary asks Vincent if it was true that her father killed his own brother. So that in itself tells me that there was "whispering" talk of this over the years and that even she eventually suspected that there was some truth to what she had heard.
Don Cardi
