Thanks for stopping by my query!
Dear Agent McAgent,
Seventeen-year-old Ky Abelson only cares about two people in the world, and one of them will soon be dead. When Ky’s brother, Tristan, is sent to the ICU due to a strangely aggressive cancer, life couldn’t get any goddamn worse. Until Ky is attacked…by himself. A grey-skinned, alternate reality version of himself that holds him at knifepoint and asks one question:
Where is Tristan?
Armed with a bat, Ky’s hearty blow [just a grammar thing here, the subject of the sentence is "Ky's hearty blow" so it sounds like "armed with a bat" is describing that, but it really should be describing Ky. Also hearty is an odd word choice to me. I'd think something like desperate or violent, etc. would convey the danger better] sends his double fleeing through the window. When he [Ky or the double? it's unclear] leaves behind an otherworldly metal fragment, it quickly becomes Ky’s obsession. Enough that his boyfriend Austin—the second most important person to Ky—is beyond concerned ["beyond concerned" sounds too weak for this]. Austin’s clear about thinking [this wording is a bit awkward. Maybe "Austin knows the fragment is just another unhealthy way for Ky to..."] the fragment is another way for Ky to fixate over Tristan. Another roadblock for the romantic future Ky promised in a faraway city. Another, and possibly his [whose?] last, round of heartache. But Ky’s damn sure the fragment can give him a clue why his double is searching for Tristan. And it does.
Briefly, it shows images of countless alternate reality Tristans—all dead.
Ky’s Tristan is next on the list, and suddenly, Tristan’s strange cancer is looking more like an interdimensional assassination attempt. Now Ky’s [I don't love the 's as a contraction of Ky is...you used it a couple times here, it might just be my personal preference though. It trips me up because it looks like a possessive] backed into a corner disguised as a choice: Find his double in the vain hope of saving Tristan and risk losing Austin or move forward with Austin and do the unthinkable, accept Tristan’s inevitable death. [I don't think it's been made clear enough that saving Tristan and being happy with Austin are mutually exclusive]
I can tell you've worked on this a lot and I think it is almost there. Most of my comments are minor. Good luck!