For more than 40 years, Robert De Niro, 76, and Martin Scorsese, 77, have been making movie magic. But when the powerful pair first teamed up for 1973's Mean Streets, they could have never imagined it would lead to a lifelong friendship. "I consider myself very lucky to have that long of a relationship with him," De Niro tells PEOPLE in this week's issue of Scorsese. "I can't imagine my life without it." The two have now worked together on nine films including their most recent Netflix mob drama The Irishman, which costars Al Pacino and Joe Pesci and is nominated for 10 Oscars . . .