Clearly, the two main characters are a boy and a man. The boy could be of any age, say from a young child to a teenager. The man is most likely an adult, perhaps in his twenties or older. They are the central figures around which the story is built, and their interactions, whether positive or negative, will drive the plot forward.
The main characters are a boy and a man. The boy may be naive and full of dreams, while the man is more experienced and worldly - wise. Their personalities and the way they respond to each other will be crucial in the story. For instance, the boy might be curious and ask the man a lot of questions, and the man may either be patient and answer them or be dismissive. This dynamic between them is what will make the story interesting.
It's possible that the main character is a young boy who is on the verge of puberty. Alongside him, there could be his family members, such as his mother who provides emotional support and his brothers who he might compete with or learn from. There could also be a teacher or a coach who plays an important role in his growth and transformation.
The main characters are the man, the boy, and the donkey.
The boy is probably a young, naive character who is still exploring the world. The man, on the other hand, is more likely to be someone with more life experience. He could be a father figure, a teacher, or just an older acquaintance to the boy.
The main characters are the old man, the boy and the donkey.
There are three main characters in this short story. First, there is the man who is likely in charge or at least an adult with some authority. Then there is the boy, probably accompanying the man. And of course, the donkey which is the focus of their actions and the source of all the various reactions from other people in the story.
The main characters are, as the title suggests, an old man and a little boy.
Obviously, the old man and the boy are the main characters. They are the central figures around which the story is built.
The main characters are, as the title suggests, the old man and the little boy.
The two main characters are a boy and a man. Given the title also mentions 'banner in the sky', they might be characters whose lives are somehow intertwined with this banner. Maybe the boy is young and naive and the man is more experienced, and they both have a role to play in relation to this banner in the sky, whether it's a physical object or a symbol in their world.
Not having read the 'Fat Man and Little Boy Novel', if it follows the historical narrative, there could be characters representing the ordinary people affected by the development and dropping of the bombs. People in Hiroshima and Nagasaki who had their lives completely changed. These could be among the main characters as the novel might show the human side of this historical catastrophe.