I imagine Quentin as a man who seems put together, but is very much a scatter brain. He has structure to his life in an educational aspect, and is the older brother that the siblings look up to. His brain is a mess, as he is constantly skipping around while talking and flipping through his past memories. There is something deeper going on though, some sort of torment. We are only given a little glimpse into what this might be, but my guess is there is an obvious mental illness. We know from the first chapter that he is dead, so it makes me wonder if there could have been a mental illness- suicide situation involved with Quentin. He is also very concerned with Caddy, just as Benjy is. Quentin wants to protect his younger sister and would do anything for her to be happy, even if that means lying about incest. Benjy more admires Caddy in the sense that he looks up to her and enjoys her kindred spirit. The difference between the two comes down to the tone of their narration, where Benjy has a sweet and innocent tone, and Quentin has a harsher, more protective perspective.
When Quentin describes the times with his father, he is the eldest son receiving life advice. Father is bestowing valuable information to Quentin with the intention of his following. Quentin takes on the role of being grown up and taking on a mans role. He seems mighty, yet childish in the way he explains how his Father told him. There is something very immature about the way he narrates even though this could be a significant moment in his life. In this scene, he is most concerned about Caddy's virginity as his father explains how virginity was created by the man, not the women. His thoughts reside in the past while explaining this memory he had with his father.