Author's Note: Man, it's been a long time since I uploaded anything. This popped into my head the other day. Envy's jealous of humans and Wrath was once human which means not only the fact that he can age as a homunculus, but a few other things that I plan to go into detail about in this oneshot.
Humanity
When Father introduced their newest sibling and the last of the seven deadly sins to the other four homunculi (Greed had long-since ran off a couple hundred years ago and Sloth was still digging the tunnel under the country), he didn't hide the fact that Wrath (that's what he was called) was once a human and that he had been turned into a homunculus so that he could rule over the humans and ensure that all the crests of blood were completed on time for the Promised Day. Nobody asked why or questioned Father, but Pride did purse his lips and scowl a little at the new homunculus. He had always been the homunculus in charge of keeping an eye on the humans and now this upstart was taking his place, but he did not argue. He understood that with the appearance of a human child, there was no way he could be certain that all the crests of blood would be filled on time, even if he didn't like it. The oldest son remained quiet and nobody dared protest if he didn't, for he always was Father's favorite.
Facial hair. That was one of the first things the homunculi noticed about their youngest brother. None of them had ever had it except Envy when he chose the form of a human who did happen to have facial hair, but that was different. It didn't grow from his own skin and Father's beard didn't ever grow either. Even Father was surprised by this development, but he hadn't known what would happen, it had never been done before. He supposed that the growth of Wrath's facial hair suggested that his cells were still growing and dying which meant that he would age. This was a fine development indeed (and was one of the desired effects), for it would look rather suspicious for the leader of a country to never age. That's why Pride kept transferring from one political family to another after a long enough absence of time. But Wrath had caught Gluttony and Envy staring stupidly at the black stubble on his chin one too many times for his liking, so he taught himself how to shave since the scientists hadn't seen fit to do so. Needless to say, the end result wasn't pretty and they learned something else about their peculiar little brother.
Homunculi wounds heal and limbs and bodies regenerate as soon as they're lost. So they didn't know what 'scabs' were when Wrath appeared before them with the lower half of his face all cut up. On the plus side, his facial hair was gone, but now they were staring at his scabs (apparently that's what they were called. Also, apparently among normal humans, cutting yourself while shaving was a pretty common occurrence among those who were new at it, though he couldn't understand why they had been so friendly and... jovial about it. It wasn't exactly a fun experience). Wrath did not enjoy this scrutiny. It was like... like being... a cornered wild animal or... an animal in a cage... something like that. He wasn't quite sure on his similes yet and don't even talk to him about idiomatic expressions.
When his children came to him about this new tidbit of information, Father was more than a little concerned. If his wounds, as insignificant as they were, weren't healing, then the philosopher's stone must have been depleted of souls in which case Wrath should have died. But he hadn't, and he did have the ouroboros tattoo upon his left eye which was a clear indication that he was indeed a homunculus. This was troubling. What good was it to have a homunculus in a seat of power if he couldn't regenerate his wounds? Regretfully, he couldn't start over and make a new Wrath. The philosopher's stone that had been the essence of his wrath had been injected into his new son who was once human and there was little if any of the original stone left in his body. It must have been destroyed when his son's body had tried to reject it. Because of this, he could not simply pull the stone out of his body and remake Wrath as he was. Well... he would just have to wait and see what his youngest son could accomplish. But for now, he had children standing before him and waiting for answers.
"It would seem that your youngest sibling is in possession of only one soul and that the philosopher's stone in his blood is enough that he has been given the Ultimate Eye and an imperfect immortality. It is my presumption that perhaps in the face of death by succumbing to the stone, his body chose to overcome it instead. So essentially, Wrath is a homunculus in name only. He cannot regenerate or heal himself and he will eventually die of old age if given enough time."
Father had never spoken about how he had created an aging homunculus before and it was interesting to hear, but still, they said nothing. They parted ways, Pride's shadows retreating back to his container, Gluttony waddling after Lust wherever she was planning on going, and Envy left on his own accord, not following after them for once, but taking his own path. When he was within the maze of pipes and tunnels well out of Father's earshot, Envy yelled aloud and punched the wall to his right, leaving a decent-sized dent in the wall and creating a huge shuddering racket that upset the chimeras roosting in the grates above. But Envy didn't stop there, he continued to beat up the wall (seriously, what did it ever do to him?) until it was nigh close to collapsing and then he started in on the opposite one. Yet even after punching the walls to death, Envy still couldn't lose the frustration he felt.
He hated him! Their new 'sibling', Wrath! Could they even call him a brother? Father had just said that he was a homunculus in name only! Which meant that having Wrath around was like having a human in their midst!
Initially, he had not hated him. Thought him strange, yes. Considered him something possibly unwanted, yes. Didn't trust him, yes. But not downright hated him. Now though... Now was an entirely different story! Envy hated Wrath because he was human and had something that he could never have. Humans...no matter how often they were knocked down or just fell flat on their faces, they somehow managed to pull themselves back up and continue living for the future... even with all the wars they had fought, slaughtering hundreds to thousands of people in the name of god, gold, or glory, they still clung to their stupid idealism and pushed on ahead to make a future that most of them would never see! They survived and they lived! That's what it meant to be a human! And it was the longing desire to struggle to live and feel that relief and joy that comes from having succeeded! He wanted that! But he couldn't have it!
And Wrath... his human-based 'baby brother'... he had it. Envy understood exactly what happened now! When confronted with the power of the philosopher's stone, Wrath's human body tried to reject the invasive object... his soul fighting to preserve his life against the hundreds of other souls within the stone until it was the only one left within the body again and had become the master of the philosopher's stone. Wrath's soul had fought and struggled to preserve itself and had survived! Wrath had it. He had retained his humanity. Now he was a homunculus with that one enviable human trait that could not be replicated or purchased. Envy wanted it. But he could never have it.
I figured that as the most human of the homunculi, Envy would despise Wrath because like any human, Wrath must also fight to survive and has been doing so since the beginning, even to become a homunculus actually. That's right you little green worm! Envy the epicness that is King Bradley! (by the way, I absolutely love the guy! He's my favorite villain in FMA! XD)