Let’s say that each of the two have never communicated or met with the other. How likely is it that the two writers will end up creating similar characters and story?
If they have similar interests, watch the same kind of movies, and read the same genre of books, the likelihood is considerable. Both will have had their imaginations saturated with the same kinds of characters and plot lines and settings. If these two people are the same age and ethnic group, living in the same country, the chances are even greater because they will have grown up with the exact same movies and books and world events. Most likely their schools used the same or similar text books, forming minds and vocabularies that work along similar lines. Personal lives and families would most likely be different, allowing for some differences, but you can see that the chances of two people creating similar novels with similar characters is quite possible. In fact, I think I’ve read some though normally I like one better than the other. Each human being is unique when it comes to talent and putting words on paper. In addition, these two people would probably not be using the same publishing house and editor; publishing house and editor add to a book’s overall tone.