Benjamin's dad, Mr. Braddock is a rich attorney. He doesn't seem to be a particularly bad guy, but Benjamin seems uncomfortable with his affluence. (That doesn't keep him from accepting the Alfa Romeo graduation gift.) Mr. Braddock has a habit of unintentionally embarrassing Benjamin, as parents tend to do. The scene where he parades Ben out before the guests in his scuba outfit was familiar to young audiences as one of those mortifying experiences your parents supply you with from time to time.
Mr. Braddock represents the voice of conventional thinking and common sense. When Ben says that he's going to marry Elaine Robinson, even though she doesn't like him, his dad says, "This whole idea sounds pretty half-baked"—which it does, obviously. And he also asks Benjamin why he's spending so much time drifting in the pool without getting a job or doing any work—another reasonable question.
Apart from asking Ben if he's applied to graduate school and wondering what those four years of college were about, anyway, Mr. Robinson doesn't give Ben any real guidance. He asks him what's wrong but doesn't follow up on it. He doesn't help him think about what might be meaningful to him. He sees the world through a particular traditional lens, and if others see it differently, he doesn't have much to offer them.
To his credit, though, he's a generous dad and has a lot of longtime friends—friends who seem to appreciate and value Benjamin. He seems to be something of a party guy. He's proud of his boy but doesn't quite understand him.