Throughout The Plague of Doves, how do Billy and Corwin Peace evolve as characters?

Throughout The Plague of Doves, Billy and Corwin Peace evolve in opposite ways. While Billy becomes a cruel tyrant, Corwin eventually grows from a troubled youth to a talented musician.
Billy Peace
As the younger brother of Maggie Peace, Billy starts out as a shy yet principled young man. When Maggie becomes pregnant with John Wildstrand's child, Billy overcomes his shy demeanor to demand that John treats his sister fairly. He is drawn into John's kidnapping scheme, and enlists in the military to avoid being arrested. War alters Billy's character, and he develops a fanatical perspective on religion that leads him to form his own cult. Billy changes from a shy youth to a charismatic religious leader, and he exerts absolute control over his congregation as well as his wife and children. He soon becomes abusive towards his family and dies at the hands of his own wife.
Corwin Peace
Corwin is the illegitimate son of Maggie Peace and John Wildstrand. He is also Billy Peace's nephew. As Corwin grows up, he develops a mean streak. He mercilessly bullies Sister Mary Anita Buckendorf, his school teacher. Sister Mary Anita has a severe overbite, and Corwin leads the other children in referring to her as Godzilla. His bullying tactics reach their peak when he sets a wind-up Godzilla toy loose in class to mock her.
Despite his cruelty, Corwin wins the affections of Evelina Harp, his cousin and a kind young woman who works at the diner. Evelina is one of many reassuring figures in Corwin's life who invest in him emotionally and try to pull him away from the dangerous path he is headed down. Nonetheless, Corwin begins using and dealing drugs as a teenager. Corwin's delinquent behavior culminates in the theft of Shamengwa's violin. He is charged and arrested. Ultimately Shamengwa rehabilitates Corwin and teaches him to play the violin. Music is a crucial part of Corwin's transformation, and he eventually becomes a talented player.
While similar in their troubled origins, Billy and Corwin undergo vastly different transformations throughout The Plague of Doves. Billy begins as a good-hearted young man and turns into an abusive shell of his former self. On the other hand, Corwin evolves from a delinquent youth into a thoughtful and talented musician. It is worth noting that Shamengwa's compassion and interest in Corwin's life played a large role in keeping him from going down the same path as his uncle.