Can you give me three examples of guilt in Crow Lake?

Mary Lawson's 2002 novel Crow Lake explores the aftermath of four children of varying ages being orphaned by the death of their parents. Guilt and responsibility are prominent themes in the novel, especially as it relates to the young protagonist, Kate, and her older brothers, Matt and Luke.
Despite offers from different family members to care for the children, Matt and Luke decide to alter their life plans so that the children can all stay together. This includes Luke deciding to forgo his plans to go to college so that he can work and help in raising Kate and Bo. Luke's sacrifice suggests a massive amount of responsibility placed on him as the oldest sibling, as his guilt at leaving his brother and sisters prevents him from attending college.
A major way that guilt is presented in this novel concerns opportunity and accepting opportunities. While Kate has been able to pursue an education in her chosen field, her brothers were unwilling or unable to pursue theirs. This results in Kate feeling guilty for her own achievements. Analyzing how Matt and Luke are affected by their own rejections and losses of opportunity would be helpful here.
As perhaps the final example of guilt in the novel, Kate realizes that her tragic perception of Matt and his life is largely constructed by her childhood psychological reactions and guilt. She sees that she doesn't have to harbor these painful feelings about her brother anymore and that doing so would only prevent the mending of their relationship.