There could be other Pokémon like Pikachu. Pikachu could be their friend who helps the little brother adjust to the new world. He could also offer some comic relief in the story. Another possible character could be Ash. Ash has a lot of experience with Pokémon, and he could offer some guidance to Mewtwo on how to take care of his little brother.
Maybe Bulbasaur could be a character. Bulbasaur could be the little brother's playmate. They could explore the forest together and discover new things. Professor Oak could also make an appearance. He could study the little brother's unique abilities and offer some scientific insights. And there might be a wild Snorlax that they accidentally wake up, leading to a mini - adventure where they have to figure out how to get Snorlax to go back to sleep.
Charizard might be in it too. Charizard could be a sort of mentor figure to the little brother, teaching him how to be strong. And of course, there could be some villainous Pokémon like Team Rocket's Meowth. Meowth might try to trick the little brother into doing something bad, which would then lead to a conflict that Mewtwo has to resolve. Also, there could be Nurse Joy, who could take care of the little brother when he gets hurt.
Perhaps in the fanfiction, the little brother has some special abilities that are different from Mewtwo's. This causes a bit of a stir in their world. Mewtwo has to help his little brother understand and control these powers. They might face some villains who want to use the little brother's powers for their own gain. Mewtwo and his little brother would then have to fight together to protect themselves and their world.
Well, the story could be about Mewtwo's little brother being created in a similar way as Mewtwo. Maybe he has different powers or a different personality. He could be more naive and curious about the world compared to Mewtwo who has already gone through a lot. And they could go on adventures together, facing challenges and learning about each other.
Obviously, Neji himself would be a very important character. His actions and words would have a great influence on his little brother. Also, other members of their clan could be main characters, like their parents or other relatives who play roles in the little brother's life and ninja training.
Ash could be one. He has a way of befriending all kinds of Pokémon, and his encounter with a friendly Mewtwo would be an exciting story. He could learn a lot from Mewtwo's psychic powers and wisdom.
The relationship could develop in a very emotional way. Mewtwo's little brother could be a source of warmth and hope for Mewtwo, who has seen so much darkness. Mewtwo would gradually open up to his little brother, sharing his past traumas. In return, the little brother would offer unconditional love and support. They would become inseparable, and their bond would be unbreakable as they face the challenges of the Pokemon world together.
Giovanni, the leader of Team Rocket, can be a very interesting character to include. His power - hungry nature and his past interactions with Mewtwo can add a layer of complexity to the story. There's also Misty. Her feisty personality and her skills as a water - type Pokemon trainer can bring a different dynamic to the fanfiction, especially if she teams up with Mew and Mewtwo or has some sort of rivalry with them.
Obviously, the two Mewtwos are the main characters. They are the ones whose encounter drives the story forward.
I can't say for sure without reading it. But there could be his friends, like a nerdy sidekick who helps him with his studies or a sporty friend who encourages him in extracurricular activities. There might also be a strict teacher who at first doubts him but later becomes his mentor.
Perhaps a new trainer who has a unique ability to communicate with Pokemon on a deeper level. This trainer, despite being new, has an innocent and pure heart. They see Mewtwo not as a monster but as a Pokemon in pain. So they step up to try and soothe Mewtwo's rage using their special gift.
In a'mewtwo meets mewtwo fanfiction', it could start with the two Mewtwos being summoned by an unknown force. At first, they are confused and defensive. As they interact, they find out that their memories of creation and the pain of being experimented on are very similar. They might then decide to search for the source of this unknown force together. Along the way, they face various challenges, like other powerful Pokémon trying to stop them or humans who fear their combined power. But through their shared experiences and newfound bond, they are able to overcome these obstacles.