Since it's called 'the twin stars story', the twin stars themselves are likely to be the main characters. There might also be other supporting characters like their friends or foes who play important roles in the story, but without more information, it's hard to be certain.
Given the title 'the twin stars story', it's reasonable to think that the two twin stars are the central characters. They are probably the focus of the narrative, with their personalities, actions, and relationships driving the story forward. There could be other characters in the periphery, such as those who guide the twin stars, or those who oppose them. But until we read the story, we can't be entirely sure who all the characters are and how they contribute to the overall plot.
I don't know for sure, but I assume the two twin stars are the main characters.