The main dupes (Rexter Dave Sarah Nono Logan aria) were chosen by the main dupes that came before. How it works is basically they have to choose 6 random humans to be the next mains..but there is one rule and it is that the human must look similar to the dupe that chooses. How they turn into dupes is by going through a unstoppable fate which is why you see ALOT of that when it comes to story about their past life’s