Antonyms for the phrase "are rivals" could include "are allies", "are friends", or "are teammates". These opposing terms suggest a sense of cooperation and mutual support, rather than competition and opposition. By using these antonyms, we can imply a positive and collaborative relationship between individuals or groups, rather than focusing on their differences and conflicts. For instance, we might say that two companies that were once rivals have now become allies in a joint venture, or that two sports teams have put aside their rivalries to work together towards a common goal. Ultimately, antonyms for "are rivals" offer a more hopeful and harmonious view of human relationships.