To set up my question, a few stories:
I heard a story about a woman who went to St. Pio (Padre Pio) to have her confession heard. St. Pio chased her out of the confessional. When she later asked her why, he told her that he had had a vision of her three sons in Hell and that it was because of her permissiveness.
Another story I heard regarding St. John Vianney: Satan was complaining about him to somebody, saying that if there were just three people on Earth like St. Vianney that the gates of Hell would have to close because there would be no more souls being lost.
A third story (which I will attempt to recall) I heard from Fr. Corapi was about Archbishop Fulton J. Sheen and (I think) Joseph Stalin. Both were altar boys and both at one point accidentally dropped a chalice during Mass. When Sheen did it, he was forgiven but when Stalin did it he was berated.
So now to my question: I know we are responsible for our own sins, but can a soul also go to Hell/Heaven because of the sins/virtue of other people? To what degree does a person’s environment and interactions with others infuence their chances for salvation?