Utterly intriguing, and well crafted. Not only did it keep me wondering (as I didn’t read the title until later in the text, when stumbling across the word Twin), but it alerted me to a perspective I had never considered, and which has a poetry all of its own. Biology can at times be a cruel leveler, it is true. What an accomplished piece of flash fiction.
May I share a fabulous flash fiction tip/suggestion you might like to explore? Diclaimer, though: by no means is this mandatory, your story worked beautifully as is, just a suggestion for future consideration, if you like.
Have a look at what I did with this story as an example.
Try piquing the reader’s curiosity with absolutely no hints what the subject/theme may be about until you reached the very end, it can sometimes work wonders, depending on what purpose you are writing with, and it’s also super fun & challenging from a writing perspective.