how is selflessness and any other hero traits used in my sister's keeper book

Consider the theme of family relations. The author shows how much complexity and difficulty is added to the relations between the family’s members, when one of them has a serious illness. The reader sees how Sara and Brian relate with each other: their daughter’s illness hasn’t broken them down, they keep having deep love to each other in their hearts. Their desire to save their ill daughter outshines their parental “responsibilities” for their other children, but their life changes in that way that they realize how much each of their children is important and valuable for them. Relations among children are also vividly depicted in the story: it’s impressive, how sincerely and devotedly they love each other, they don’t take into account that their parents pay more attention just to one of them.