In my work with adolescents, I see rivalry most often fueled by differences in developmental stageswhat a 14-year-old needs for independence may clash with an 8-year-old's need for closeness. When siblings are competing for the same limited resources, whether that's parental approval or attention, tension naturally follows. I recall one family where charting out family responsibilities visually reduced conflict because it gave each child ownership without comparison. When rivalry hit them hardest, structure and clear expectations saved the day. I usually suggest parents create routines that spotlight each child's strengths, so competition slowly shifts toward cooperation.