I think the narrator in this excellent story clearly understands his alienation and the way that he is suffering just as his brother Sonny has suffered, although the root cause of that suffering is very different. The narrator becomes very aware of how the loss of his child impacts his own life, and by the end of the story such evidence of suffering is something that seems to be caught up in some kind of universal woe that Sonny's music taps into and expresses. The way in which the narrator describes Sonny's music and how he uses it to transcend this suffering gives ample evidence of the way in which the narrator, and his brother, can overcome the alienation that they face:
And Sonny went all the way back, he really began with the spare, flat statement of the opening phrase of the song. Then he began to make it his. It was very beautiful because it wasn't hurried and it was no longer a lament. I seemed to hear with what burning he had made it his, and what burning we had yet to make it ours, how we could cease lamenting.
The brother crucially experiences something of an epiphany at the end of this story as he finally hears his brother play the music that he dedicated his life to and that led him into such difficulties. Through hearing his brother's music, the narrator comes to understand his own alienation and suffering so much better and is able to find strength to potentially overcome it.