In order to more efficiently breed their army, Nifleheim engineers their MTs to be Alphas, Betas, and Omegas. Too bad whoever got Prompto out of Nifleheim forgot to send that memo along, so poor Prompto has no idea WTF is going on with his body. Insomnia's doctors have no idea either, giving him a diagnosis of "some kind of intersex, we think, maybe, IFK" and putting him on all sorts of hormones, some of which help, some of which land him the ER. Prompto ending up pregnant and needing an abortion because no one knew he could even get pregnant, much less how safe a pregnancy would even be for him. Prompto being insulting slurs like ladyboy. Protective bros who are just as Prompto is by his body's changes, but refuse to let him go through it alone.
Prompto/Any, Omega!Prompto, only MTs are A/B/O