Does such a thing really exist?
I think, if you look for such an answer here, you may have suffered traumas in your childhood and you are looking for solutions and answers to your suffering,
In any case yes, it exists in some individuals. I speak by direct experience here.
The inner child is a sense of wonder and curiosity about life and the world.
Yes, this is recurrent in "normal" people so to speak.
When a person lives a very heavy trauma in childhood, even repeated, like abuse and the such, the mind may react in "emergency procedure" ways to ensure survival of the person.
This is called PTSD , Post Traumatic Stress Disorder.
In short : the mind chooses to separate you as a child, from your main self. The mind builds the idea you are NOT that child anymore, because you suffered too much, and the "you" is discarded and put in a subconscious area of the mind where all the related memories are sort or forgotten. Otherwise the person would suicide, go mad or worst.
This leads to the creation of a sub-self, that remains hidden in your mind, repressed. But still lives. In short, the inner child is made of repressed emotions, stored in a subconscious area of the mind. So we have a wounded inner child.
I worked on this also with my GD for about a couple of years, that lead me to healing of this part of the mind, by positive experience, studies and meditation.
My mind was so wounded that I even, unwillingly, created a thoughtform. That thoughtform was indeed a child, created my my own mind, to "discard" that part of me who was severely wounded. I put the psychic energy in something "external" and I really created it. It was a huge problem as this thoughtform was connected (like an egregore indeed) to my father and picked up a lot of negative emotions, transferring those emotions to me and causing life to derail sometimes, and other problems.
In short. I needed months to build the idea in me, that I WAS that child, to re-accept that part of me in myself. By elaborating with inner dialogue in trance (you may use self hypnosis), and visualization, I gradually transformed this "child" from an external "waste" to "myself years ago". That thoughtform gradually vanished, as I was not feeding it anymore.
At a certain point I felt that "child" was again in myself. Then I healed it like you can read
in this post
After that point, I felt like Seeker in the Dark relates : I found again my sense of wonder, I'd say an emotional part of the mind that I lost. SO the "child" is not a separate child anymore, it is simply ME and a part of my mind that I integrated in me, as it should be.
This cannot happen without the guidance of a Demon, as they did with me, leading to positive and healing life experience, like a Demon can do by creating events.
So, yes, under some circumstances it exists.
You may want to read books from Bessel van der Kolk, like The Body Keeps the Score, to understand how traumas work in the mind, and heal them in case you suffered one or more, that lead to your inner child to live a separate life from your main self.
Be it your case, I feel sorrow for your situation, I know how this can be hard.
In case always remember : it was not your fault. It never is. Children are innocent, cannot be blamed if they received violence or traumas.
Take care.
If you feel the need to vent out or talk, write here. You will be listened.