Hi Peaches,
There is something called co-consciousness, whcih may relate to what you are describing. I used to have some links to info about this, but I can only find this one at the moment:
http://www.geocities.com/HotSprings/8089/multi2.html
I spent time researching this because of my own experiences. When I am under great emotional stress I will sometimes experience a change in consciousness. I can feel it coming on, my brain seems to spin inside my skull, my eyes don't want to stay open, and if I make them I can't see properly. Sometimes I will feel like I don't understand English. I usually find some way to pull out of these experiences because they are very frightening (standing up and moving around, or forcing myself to read something often works). If I don't do that however, I will find myself becoming 'younger'. My posture, body language and speech, even my thoughts will no longer be my own, but the me I usually am is aware of all of this, and is watching from somewhere in the back of my head. There are several ages of younger me, each with a different feeling tone. The youngest seems to be preverbal. Two are boys. Once one of them is in the foreground, I can usually regain control by putting whoever it is to sleep.
I do everything possible to avoid these switches, and I seldom talk about them. I am not even sure I have said anything to my current therapist about it. Sometimes I am curious to know what these kids (that's what I call them ' 'my kids') have to say, but the whole thing is so scary and feels so absolutely out of control...so I don't go there.
Hope this helps...
Oh...I have no memory of trauma that seems significant enough to have created this...but then who knows really what causes what?