The little meltdown fredo had when michael had to tell him to play his position shows that he didnt want Michael around. Even back when, despite michael being younger, Fredo knew he was micheals son. Its like someone whos lazy on the job and suddenly a new quiet, hard working and serious guy comes on the job. Hes a threat, that you can see immediately.
Well Vito didn't want to admit it, but he knew Fredo was probably gay. There were hints that Fredo was, but it was not explicit said. Not to mention that Vito was smart, and wanted the world for Michael, because he saw him grow up to be his own man. His grandplan was to never involve Michael into the family business. That's why Michael was special to Vito. Vito saw Fredo as a weakling, which was not a bad thing, just not the person to run the family business. In the end Fredo wanted to be respected, a person who didn't need anyones help. Sadly though Michael's lust for power ended up killing Fredo when he should have just forgave him.
Being said though, John Cazale was the Stockton to Pacino's Malone. Cazale loved playing the weak person, because he made Pacino better. He died of Cancer way too young in his life, but he was husband to Maryl Strep.
RIP JOHN CAZALE



he was just soft. moe greene slapped him for knocking down too many cocktail waitresses