Which sentence would make the MOST effective concluding sentence for an essay on sibling rivalry? Sibling rivalry hurts brothers and sisters. Sibling rivalry may be unavoidable, but by learning to value each individual's strengths, its harmful effects can be minimized. Sibling rivalry creates competition, jealousy, and frustration in familles. Sibling rivalry causes many problems, but the worst is the frustration that it creates in familles. ​