Look at Shameless . The Gallagher siblings are constantly at war. Fiona wants to leave; Lip feels trapped; Ian is trying to find himself; Debbie just wants to be seen. They steal from each other, lie to each other, and sabotage each other’s relationships—but the moment an outsider threatens the clan, they unite with terrifying ferocity. This push-pull is realistic. In complex fiction, a sibling is not just a rival; they are the only other person who remembers the smell of the old house, the sound of their mother crying, or the violence of their father’s temper.