Being rivals implies a competitive relationship between two or more parties. Antonyms for this word can include "being allies," "being friends," "being cooperators," or "being partners." These words convey a positive relationship where parties work together towards a common goal rather than against each other. Being allies means being supportive of one another's interests, while being friends is a bond of affection and trust. Being partners refers to a cooperative relationship where parties share resources and collaborate to achieve mutual benefits. Finally, being cooperators implies a joint effort towards achieving a goal, without any competitive interests. Therefore, the antonyms for "being rivals" suggest a positive relationship based on shared goals, interests, and trust.