Well, I trust the story-basis of behind the scenes and I know the other players will not meta-game this knowledge. But in this world, the actual truth of the survivors of the cataclysm that nearly destroyed all life was in the low thousands at best. The majority of humanity was spread thin between two constructs within the gray era. The first attempt was an obvious failure as their escape to another planet came up short with limited resources, manpower and other facilities that space could not always provide. Scrapping that project, the corporation started on another project. Known as the "Seed". Essentially what this was, is a series of self enclosed habitats where humanity can flourish and go on their daily life.
[Gray Period: Classified To Citizens]
But, along the lines, the remaining developers went mad in their design, instead of building a new safe haven, they built a series of self replicating machines which the rest of the "real" humanity could lord over and control the rest of the world like ants in an ant colony [See God-Complex]. The breeding procedure was first a few failures as a few remaining survivors [of lower class standing] were used under harsh breeding campaigns and other grotesque mockeries in an attempt to extend life [Hence the coming of the Corpse Soldier, not really a live being, but they provided how sick the human mind can be and used these "living" soldiers to fight for boredom and over other small corporations that remained.].
The group themselves with discovery [and madness] found a strain, of hidden potential. Basically a pandora's box to even to them today, that unlocked the potential for psionics. They did succeed in some form, but the recipients with the gene therapy ended up eighty percent of the time going completely insane. But that didn't stop them, but all of including them in the populous as a whole. Breeding them for their own gains and then interbreeding with them to create the race stronger. Soon there was a war between corporations where the corporations fought over rights of this new discovery and Rokujou Inc. ended up the victor after cannibalizing other remaining corporations. Now with this new knowledge and pandora's box still being peeked into, they found ways to create other life-forms and how to keep other traits at bay, keeping the spoils for themselves.
Over the course of selective breeding, even amongst themselves they finally figured out all they needed to know to replicate human traits and breed people without the usage of copulation. Eight women were chosen and hard-wired into central hubs at the center of the development center to give constant birth ever so often of these genetically augmented people. Thus created the self sustaining cities that birthed the first "Adam and Eve" of the new age while the corporation stayed in the background as the "new government" to aid life into. As with all of this hidden potential and pushed aside, the first Nephilim was born out of accident. SPE#3318-76SERA. She was a special case as her genetics caused her to have memory lapses of another being that was written in the code via "error" [no one knows how it happened, fate perhaps decided to intervene]. She was kept largely in captivity and used for intense experimentation in the city of Lyran, developing her latent psionic skills and apparent inability to die, only seeming to reincarnate. Seeing as to profit over this new discovery, they made new models based off of the original for profit amongst their new pawns and to see if Nephilims were going to be the next stage in humanity.
[End Gray Period]
As for people born free, they're all submitted and a part to the drudgery that all citizens [both high and low] go through, but the seeds of discord was interwoven within their genetics as a part of a failsafe that the corporation could not overwrite or completely take out, only suppress. So various individuals will show traits of moderate to light inherent fault and self-will, but once one completely finds an error in it's current set paradigm, it will completely awaken as a babe finds the difference between reality and fantasy as it matures. This is set over all of the creations, human, Byt and Nephilim.
As for cross-breeding between humans and Nephilims, it has yet to be successful at all, as the genetics in the Nephilim do not accept the seed or fertilize the egg in the right way resulting in grotesque mutations, stillborns and failed births. The only Nephilim capable of breeding with humans was SPE#3318-76SERA, which created her child ZIV in the process.
Now for the span of life, Nephilim life is vastly longer then humans and they have just been introduced En Masse, at the end of the written series, Sera is close to eight hundred years, now she was the longest lived and have produced various other results, in other sense, she is the living Goddess of her race as a whole. [As well, resulting in a lot of the original members of the corporation leaving their ancestors to rule and as well, losing a lot of information in the process of how exactly the relic devices work fully.]
Now on for the facet of humanity between the drones and the Resistance. The notice between the two are apparent and the corporation tries it's best to cull any uprising at any cost, from bribes to eventual assassination squads. As with humanity as a whole, they're seen as the proverbial bogey-man and urban legends. Things the corporation tell you of if you're a naughty child when you grow up. In reality, the only people who live in reality are those who are part of the Rokujou Inc. The Collective and The Resistance.