If that's the case, then it might not always go well with the alter egos if they are conflicting enough, and know about another's presence. If one did, they would've been communicating through a mirror, so they can see who they are talking to.
In more advanced cases, some alters will take on a "protector" role and allocate time to the others. Some alters would also be more active than others, even ones that relegate the host into a recessive role. The alters would fight, too. I've seen this happen to some people; they would become very quiet because their personalities are fighting.
Each alter sometimes has a face of its own, along with its own name. Though, to my knowledge, people with dissociative identity disorder don't spend lots of time in front of the mirror, talking to themselves. Even those who are aware of the other personalities. The personalities switch, with one at the expense of the other, so you can't necessarily hold a conversation with "the man in the mirror." If you
are able to speak to the other alters, it's usually done as a one-sided conversation, with the alters as auditory hallucinations, much like when a schizophrenic would talk to their voices.