Alright, just as I expected, focusing on just one girl made it significantly better. Still a lot of room for improvement, but it looks like you're on the right track. The story still looks rather random at times, but overall much less so and having a clearer direction of where it's going. The dialogue at times still feels like it could be written by AI… especially the part where the protagonist instructs his sister how to feel (to beg for life but not fight back) and she complies for the rest of the story as if she wasn't behaving totally differently a second ago. And overall there are still a lot of repetitions and back and forth when characters can't make their mind. Perhaps you as an author should take pauses to make your own mind first about the next section of the story before writing it.

I know some writers can just start writing whatever comes to their mind and somehow it ends up as a cohesive story. I also know I personally am not like that. What works best for me is knowing exactly where I want the story to go start from finish, which also works best with one-shot stories. The story doesn't always ends up going exactly as I planned, but having an ending in mind lets me know what I can or can't change about that plan. For example, my story Black Ice ended up very different from what I initially planned, but the ending was decided from the start where the twins would drown themselves in a specific way where they look at each other through the ice as if being each other's reflections. How they got there ended up very different, but knowing this is where they have to get allowed me to get them there anyway. On the other hand, whenever I start something longer with the idea of "I'll just start with this premise and then see where it goes", it never ends up going anywhere.

So what I'm saying is that if you see that writing spontaneously doesn't work very well for you, try changing your approach and do some more planning. Not just for the story as a whole, but also for sections of the story as you go. After finishing a section, stop for a moment to think what exactly you want to happen in the next section, and how it fits in the overall plan. Maybe what you'll write won't end up exactly what you planned, but I've discovered at least for me it works out better to have a plan and end up writing something else than trying to write something without a plan at all.