I think that some of you are envisioning Vito's construction of his crime family apparatus and its operation as an affair that took place under the noses of his family. Why think that Roth or Ola was ever in proximity to Sonny or Fredo as kids? Sonny was at least 16 before Vito admitted him to any exposure to the business and that was only because he claimed to have witnessed Vito's murder of Fanucci. Even then, as the novel states, his exposure was quite limited until the Maranzano War.