For 'Saga', Alana and Marko are the central characters. They are from opposing sides of a galactic war but fall in love and have a child together. Their journey to protect their family while being hunted is the heart of the story.
One popular work is 'Y: The Last Man'. It presents a unique post - apocalyptic world where all the male mammals except for one man have died. It's a story full of adventure, mystery and complex character relationships.
In the 'Brian Keene The Rising Graphic Novel', we can expect to see some archetypal characters. There may be a lead character who is an everyman, thrust into this nightmare of the dead rising. This character would be on a journey of survival and discovery. There could also be a mentor - like figure, someone with a bit more knowledge about the situation, whether it's a doctor or an older person with some experience. And of course, there would be the undead themselves as a sort of 'character' in the sense that they drive the horror and action of the story.
One of the main characters is Ciaphas Cain. He is from the 'Gaunt's Ghosts' series. He is a bit of a reluctant hero, always getting into and out of trouble in the most interesting ways.
As I'm not familiar with 'Brian Love Story', I can't say for sure who the main characters are. But I assume Brian is one of the main characters.
There might also be characters like his advisors. They would play an important role in helping Brian make decisions and rule the kingdom. Their personalities could range from wise and old - school to young and innovative.
There are also the various Black Templar chapter masters. For example, Helbrecht, who is a central figure in many of the stories. He leads the Black Templars with great strength and determination, and his character development throughout the novels is quite fascinating as he has to make tough decisions in the face of various threats to the chapter.
Yashiro Isana is a main character. He's a seemingly ordinary student who gets caught up in the extraordinary world of the clans.
Obviously, Torentos Brian is one of the main characters. The other main character would be the one who is adopted. This could be a young orphan with a mysterious past, or perhaps a person from a different dimension who has no place to go in this new world.
I don't know for sure as I haven't read the book. But it could have characters like a young child excited for Christmas, or maybe an old man who shares the wisdom of the season.
The two main characters, Stewie and Brian, can be portrayed in different ways in fanfiction. Sometimes Stewie might be even more devious than in the original show, and Brian could be more heroic or more flawed. Their interactions are what the readers of this fanfiction are mainly interested in, whether it's them arguing over the TV remote or teaming up to save the day.