The first paragraph demonstrates an adult looking back. The brother is remembering the short time he had with little Doodle, and how he was the “craziest brother a boy ever had.” The reflective first paragraphs show that the brother has changed his attitude now that he is an adult.
It's strange that all this is so clear to me, now that time has had its way. But sometimes (like right now) I sit in the cool green parlor, and I remember Doodle.
The child’s perspective is always slightly colored by the adult narrator, but it is clear that the narrator feels guilt while the child did not. As a child, the older brother simply felt shame and irritation with his disabled brother. As a child, he remembers the positive elements.