This story is a cautionary tale of what can happen when a sibling rivalry spirals out of control—stopping short of murder, it must be said, but transforming a son into a daughter is certainly well within the bounds of ethical competition. Whatever it takes… for the win. Enjoy!
Just to briefly pump my own tires: being an only child and thus having no experience whatsoever with siblings (rivalry or no), a story like this serves as a shining example of a powerful imagination at work (tires: pumped). As for precursors, I’ll point you to “The Game” from 2014, which is another example of a couple of over-competitive people taking things too far. These tales might not be terribly realistic, but they do make for good fiction.