Obviously, Robin and his brothers would be main characters. Robin, with his skills and leadership within the Titans. And his brothers, who would bring their own personalities and abilities to the story.
In addition to the Titans and Robin's brothers, there could be some villains in the fanfic as well. These villains could serve as the catalysts for the Titans and Robin's brothers to come together. They might be new villains that the Titans alone can't handle, so they need the help of Robin's brothers, or they could be old foes that are now more powerful and require a united front to defeat.
The other Titans members like Starfire, Cyborg, Beast Boy, and Raven would also be main characters. They are an important part of the Titans, and when they meet Robin's brothers, their reactions and interactions will be crucial to the story. For example, Starfire's friendly and curious nature might lead her to be the first to approach Robin's brothers and start a conversation, while Cyborg might be a bit more cautious at first.
Well, in the fanfic, perhaps there would be a lot of action. The Titans and Robin's brothers might team up to fight a common enemy. They could combine their unique skills and powers to defeat villains.
Obviously, the main characters would be the Teen Titans and Kid Flash. The Teen Titans usually consist of Robin, Starfire, Cyborg, Beast Boy, and Raven. So you can expect to see them interacting with Kid Flash in various ways.
The main characters from Young Justice like Robin (Dick Grayson), Aqualad, and Superboy are likely to be there. And of course, the Robin Brothers which could include different versions of Robin such as Jason Todd and Tim Drake.
In this fanfic, Beast Boy is bound to be a central figure. The other Titans, Robin, who is the leader and strategist, will play an important role. Starfire, with her alien powers and unique personality, will be there too. Cyborg, the half - human half - machine, and Raven, with her mysterious powers, are also main characters as they interact with Beast Boy and form the core of the Titans in the story.
Obviously, all 14 Doctors are the main characters. Each with their own distinct personalities, from the wise and somewhat eccentric First Doctor to the energetic and compassionate Thirteenth Doctor. Their companions could also play important roles. For example, Rose Tyler might accompany the Ninth or Tenth Doctor, and Clara Oswald could be with the Eleventh or Twelfth Doctor. And of course, the Doctors' archenemies like the Daleks or the Cybermen could make appearances as antagonists, which would further drive the story as the Doctors work together to defeat them.
Another character that might show up is Oracle. She could be the one providing information to the Titans about Robin's activities. Or she might be trying to figure out what's causing Robin's change from a distance. And sometimes, new original characters are introduced in the fanfiction. These could be other dark heroes or anti - heroes who either side with Robin in his darkness or try to oppose him, adding more layers to the story.
Obviously, Harry's kids would be the main characters. They could be the ones driving the story forward with their curiosity about their father's past and the Dursleys. And of course, the Dursleys themselves. Vernon, Petunia, and Dudley. They are important as they are the connection to Harry's difficult childhood. Their reactions to the kids would be a major part of the story.
The main characters would surely be Damian and the Titans. Damian with his complex personality, trained in combat and having a bit of an attitude. And the Titans, each with their own unique powers and personalities. Starfire with her alien strength and kindness, Raven with her dark magic and introverted nature, Beast Boy with his shape - shifting ability and fun - loving attitude, and Cyborg with his technological enhancements and sense of humor.
I think it would be Spider - Man. Since he's also relatively young and has a sense of humor. He would be able to relate to Robin on a more personal level compared to the other Avengers. They could start chatting about their cool gadgets and how to use them in different situations.
In this fanfiction, we can expect to see a lot of interaction between Jason Todd and Starfire. Starfire, being an alien with her own set of powers and values, might be curious about Jason Todd's more brutal approach to justice. Their exchanges could be really interesting, as they come from very different worlds in terms of their upbringing and experiences in fighting crime.