I think its possible even without being co conscious. I didnt have co consciousness with any of my laters from the time my first alter was created when I was three years old all the way through my oldest alter who was 18 and still didnt have co consciousness until some years later when I was in treatment for having DID. my parents, my relatives, friends college professiors and peers none of them knew I was DID and none of them saw any difference. no one knew I had alters and switched into them until I chose to tell them. then for a long time no one believed me cause they didnt see any real difference after I told them. even my partner who has known me since the 9th grade couldnt tell the difference between me aware and me dissociated cause all my alters were the type of alters that were protectors that didnt come out and say "hi there I'm popeye how you doing?" they just came out and took care of the things I couldnt handle or do on my own. my therapist told me that they didnt notice a difference cause I was DID when they knew me before my having the diagnosis so of course they were not going to see any difference after I told them I was DID. Nothing changed except the knowing what I had. I still acted the same way before and after diagnosis so they didnt know.