It could belong to a new character introduced in the fanfiction. A young hero or villain who discovers the ring's power and uses it for their own purposes.
The ring might belong to an established character from the Young Justice series, but with a new backstory. For instance, maybe it was given to Robin by his mentor Batman for a special mission, and it has some hidden features that are crucial for the mission's success. Or it could belong to a villain like the Light's agent, and they use it to carry out their evil plans.
There's also the possibility that the ring belongs to an ancient hero or villain from the past in the Young Justice universe. It could have been lost for centuries and now resurfaces, causing a stir among all the factions in the story. The race to claim the ring could drive the plot forward, with different characters having different motives for wanting it.
The ring could be a symbol of power. Maybe it gives the wearer special abilities like super strength or the power to fly. It could also be a family heirloom with a deep backstory that ties into the character's past in the Young Justice universe.
Team dynamics also play a big role. In Young Justice, the team is important. When a character has an orange ring, it can affect how they interact with their teammates. Some fanfictions might show how the team adjusts to a member with an orange ring, whether it's through trust - building or dealing with newfound jealousy or competition.
One good 'Orange Ring' Young Justice fanfiction could be on Archive of Our Own. Just search for 'Orange Ring' in the Young Justice fandom section there, and you'll find various stories. Some might focus on new adventures of the characters related to the orange ring concept.
You can use 'ring ring ring ring' as a signal for something exciting in the story. For example, in a story about a wizard's apprentice, the 'ring ring ring ring' could be the sound of a magical alarm that warns of a dragon approaching.
One bedtime story could be about a magical bell that goes 'ring ring ring ring'. The bell is in an enchanted forest and every time it rings, it wakes up the little fairies who then start their day of spreading magic and kindness in the forest.
There's no way to be certain without reading it, but perhaps there's a female lead who is somehow connected to the ring. Maybe she has a special ability that is awakened by the ring, and there could be a male character who helps her on her journey with the ring. There could also be an antagonist who wants to steal the ring for their own malicious purposes.
Ring ring bedtime stories could be a collection of bedtime stories. Maybe they are stories that start with the sound of a ring, like a doorbell or a phone ring, which adds an interesting element to the tales.
There could be a story where a boy hears a mysterious 'ring ring ring ringtone' coming from an old attic. When he follows the sound, he discovers a time - traveling device that was set off by the ringtone. He then travels back in time and has an adventure in a bygone era, and at the end, it becomes his bedtime story to remember.
It could be a unique sound associated with bedtime stories, perhaps used to signal the start or end of a story. For example, it might be a special ringtone in an app that reads bedtime stories to kids.
Since I haven't read the book, I can't say for sure. But it's likely they are the five young adults that the title refers to. They could be students, or just regular young people living in a fictional town or world.