Kyle Rayner's Green Lantern and Wally West's Flash have a longstanding friendship that flourished during their time together on the Justice League. On multiple occasions, Rayner has said that everyone in the Justice League feels like family to him, but in Brian K Vaughan and Norm Breyfogle's Green Lantern: Circle of Fire #1, Kyle is surprised to learn that he and Wally West are destined to become part of the same family years into the future.
Kyle meets a descendant who is connected to both him and Wally when she responds to a distress signal he subconsciously sends out to the Green Lantern Corps after a villain named Oblivion kidnaps the entire Justice League. Since Hal Jordan has recently dismantled the entire Corps, the call for help is sent out to Lanterns from other times, so Rayner is met by a group of Lanterns from both the past and the future, all of whom are eager to help.
Ali Rayner-West is thrilled to meet her ancestor. She explains that her father was a Green Lantern who gave her his ring before he was killed in action, and her mother is the Flash. Ali has inherited both sets of powers and calls herself Green Lightning. Both sides of her family would like to see her focus on a specific legacy, but she proudly and stubbornly chooses to juggle both sets of powers and responsibilities. She is the culmination of two long lines of heroes, and the pressure that comes with her incredible lineage weighs heavily on her, psychologically limiting her to only using one set of powers at a time.
Kyle sends Ali and Adam Strange to check on Adam's home planet, Rann, which was recently attacked by Oblivion. When they get there, they discover the people of Rann have gone mad. They are attacking each other and destroying everything in their paths. Green Lightning speeds up her sense of sight to see an otherwise undetectable light that Oblivion is broadcasting throughout Rann. She is sure that the light is what's driving the planet mad, but is shocked when she and Strange realize that the light is coming from a gigantic green lantern. In an act of desperation and inspiration, Ali runs around the planet while using her ring to divert the light. She succeeds by using her two powers simultaneously for the first time. After this breakthrough, she calls Rayner and the other Lanterns, and they all head to Oa to continue searching for Oblivion.
Oblivion is waiting for them all on Oa. He attacks them and the heroes do their best to fight back, but he is too powerful for them. In a last-ditch effort, Rayner flies right into the villain, only to discover that he is now within his own subconscious. Here, Kyle realizes that Oblivion is the manifestation of his depression and anger made real subconsciously by Rayner using the power of the ring. This whole time, he's just been fighting his own demons.
As it turns out, the other Lanterns who have been helping him don't really come from other times. They too are a product of his subconscious, each representing the positive and hopeful elements of his psyche. To defeat Oblivion, Rayner has to banish them all back to the depths of his subconscious, including his descendant Ali. Before she goes, Rayner tells Green Lightning that she represents his hope for the future. It's possible that in time, she will be more than just a dream, but for now, she exists only in Kyle Rayner's mind and as a powerful memory for Adam Strange and the people of Rann.