I am struck by the avariciousness of Vito's mother when she defended Vito against Ciccio by putting a knife to his throat. I wonder if Vito's capacity to murder comes mainly from his mother or father.

As the novel states, his father was murdered because he failed to accommodate a Mafioso, thus evidence of courage and/or stubborness (which the novel states helped shape Vito's demeanor when faced with adversity). On the other hand, his mother tried reason to placate Ciccio, but resorted to violence when reasoning was unproductive.