Thoughts as I read the story:
* Your verbiage at the start of your story is a waste of pixels. They don't give you more control/ownership of your story, etc. All it does is piss me off a little that I wasted a few seconds of my life skimming them
* Way too much narrative summary and backstory at the start of your story. We don't care that the main male character's mom had many years ago "[a] deep set look of despondency, of emptiness, of a life turned upside down." The story is about the MMC and Gabi - keep the focus on them
* A common piece of advice for short-story writing is "Start your story just before something interesting happens". The huge amount of narrative summary at the start had me skimming for the start of something interesting. I don't think there was an interesting scene on the first page. The ratio to narration to dialogue is just ridiculous
* I hated "Big Boy" as a term of endearment. Really put me off
* In an incest story, I want the sexual tension to steadily ratchet upward until the two main characters surrender themselves to their love for each other. I admit I skimmed a huge amount of the story, but I didn't see any sexual tension building. Instead, I felt Gabi offering herself was kind of out of the blue. The MMC didn't see it coming
Your writing style did not work for me. Maybe it worked for others. If you want to continue writing the way you write, I'm sure you'll find an audience for it. I just don't know how big it is.