Fleshchild/theories

Twin Theory
Under the assumption that the dreams the fleshchild haves has some origins from the original human their stolen brain came from, we can assume that the original brains came from two conjoined children. Vice and Visi (as humans) were born conjoined twins and were separated, both still have memory of this.(Mutilation effect, conjoined effect)

As there is constant symbolism of their duality, we could assume that they were not only separated, but separated from themselves for most of their lives. It symbolizes their constant longing to be with eachother again as brother and sister. (Where the doll effect is found, both representations of the twins are next to each other, and could show that the both remember playing together.)

Perhaps both of the human twins requested to donate their organs, and their brains coincidentally ended up next to eachother in the lab.

FleshSmile (FleshChild/ .flow theory)
A little theory that I (a anonymous user) have is that BOTH Vice and Visi are actually the real names of Smile and his sister (Hou). The resemblance of Smile and his sister is shockingly similar to that of Vice and Visi, but why should this be when Vice exists in a different timeline than Visi? Have you of little faith retraced your steps from were you got the head part? You will notice that both the man and woman's doors are blocked off by police tape, meaning something must have happened there too!

Maybe I'm wrong, maybe I'm right, if both Vice and Visi exists in the same timeline, maybe this is the origin story of Smile and his sister, maybe Sabitsuki once met Vice and/or Visi at one point in her life (considering that the dreams we humans have are just past events recounted by our sub-conscious)? But who knows...

IT IS UP TO YOU TO FIGURE THAT OUT...