The main character is the son who is neglected. But in addition to that, there could be antagonists. Maybe there are people who contribute to his neglect or those who oppose him as he tries to rise above his situation. Also, friends or mentors he might encounter during his journey could be main characters too. They could guide him, teach him new skills, or simply be there for emotional support. The RWBY characters that interact with him could also be considered main characters depending on how much they impact his story.
I'm not sure specifically as there could be many different takes on it. It might be about a character who is the son of a 'Winter' - related character in RWBY and is somehow neglected, perhaps exploring his journey of dealing with that neglect, his search for identity, and his relationship with other RWBY characters.
Aside from Naruto and Raven, it's possible that other RWBY characters like Ruby, Weiss, Blake, and Yang could also be important. They might interact with Naruto in different ways, either as friends, allies, or foes. And perhaps some of Naruto's friends from his own world, like Sasuke or Sakura, could make appearances in the story, which would add more depth to the interactions and the overall plot.
In addition to Team RWBY, characters like Qrow or Professor Ozpin might also play important roles. Qrow, with his combat experience and knowledge of the world, could guide the younger characters in facing the winter - related threats. Ozpin, on the other hand, might have some hidden knowledge or plans related to the significance of this particular winter.
I'm not sure specifically as it's a fanfiction and can vary greatly. But it could potentially have Naruto characters like Naruto himself or Sasuke, combined with some Tokyo Ghoul characters like Kaneki. Maybe there are also some original characters created for this fanfiction.
Obviously, Naruto is one of the main characters. Since it's related to him being involved with a neglected god. The neglected god itself is also a main character, as the whole story revolves around its relationship with Naruto. There might also be other characters like Sasuke or Sakura who could be involved in different ways. For example, Sasuke might be suspicious of Naruto's newfound connection with this god and it could cause some tension between them.
It could be that some of the neglected characters from Naruto, like Rock Lee for instance, are made main characters in this fanfiction and are paired with a Gremory character. Maybe a Gremory character who also has been somewhat overlooked in their own series. This would give a new perspective and new storylines to explore.
Well, there are several common themes. Family is often a theme, whether it's his relationship with his own family (if there is one in the fanfic) or how he becomes part of the RWBY 'family'. Redemption can also be a theme. Maybe the Son of Winter has a dark past and is trying to make up for it. And of course, the theme of growth is present. He will likely grow in power, knowledge, and as a person throughout the story. For example, he might start off as a bit of a loner but gradually learn to trust and work with others in the RWBY universe.
Another option for the main characters could be Kaiba from Yugioh. His pride and determination would make for an interesting dynamic when faced with the neglect from the Naruto world. And from Naruto, Sasuke could be involved. He might initially see the Yugioh characters as a distraction from his own goals, but later on, things could change.
Obviously, the neglected twin is a main character. They would be the focus of the story as they deal with being in Harry's shadow and finding their own place.
The jailer and an old, wise shinobi could be the main characters. The old shinobi used to be a great hero but now is retired. He sees the same potential in the jailer that he once had. He mentors the jailer, teaching him old techniques that were forgotten. Together, they face a new threat to the village that the other shinobi are ill - equipped to handle.