Why were Sith and Bab such unusual characters from the story Visitors by Sarah Ellis?

There seems to be a misunderstanding. There are no characters named "Sith" and "Bab" in the story "Visitors" by Sarah Ellis.

Could you be thinking of a different story or author? Please provide more context or the correct names of the characters you are referring to.

I would be happy to help you analyze their unusual traits once you provide the correct information.