I guess for me the essence of the 'body born' person is merely the concept of the lost potential. The potential for the typical path of the development of the human personality was there, but it didn't eventuate. I don't believe it still exists somewhere in a protected embryonic-like state.

Like you Flockpride, I believe that all alters and identity states (for that is all they are, really) are as 'body born' as any other identity state. Ultimately they are all one self - they all came from that original body born human child - but it was the *sense* of identity that was disrupted.
For when it comes down to it there are not many different people living in one body... there is ONE body, ONE mind... there was only one potential integrated human self, but it failed to integrate into one coherent conscious identity.

When I was more dissociative than I am now my disintegrated self states most vehemently denied any connection with other parts of self. They were most adamant that they were NOT "______" (original birth name).
They came around in the end, tho.