I like the description of Fredo in the novel, the child that parents pray for - loyal, obedient, loving, good-hearted, and still living at home. Fredo adored his father, and was protective of him. However, he was just not a strong enough man. So, the Don kept him close, kept him around to get the car, etc., but in no way are we given any indication that Fredo ever makes decisions.

At the wedding, Fredo is never asked to come into the Don's office as Sonny was, to learn at his father's knee. I think that's a pretty good indication of his standing in the Family.