Can other Alters appear later?

I found out 3 years ago that I have D.I.D. I'm finally in therapy with a therapist I kinda trust. I'm really working on the timeline of when the 8 alters that I'm aware of became to exist. Since working through the trauma. I have not felt quit right. Have been having uh "co-conscious" feeling. Is it possible to have more Alters that even the one's I know don't know about them?

yes they can appear at different ages. We were in our 40’s before most of us discovered we were a system and are different ages.

Any event seen as a trauma at whatever age can trigger a split of existing alters and a new one to form.

Sometimes what seems to be a ‘new alter’ may also be the result of a couple of past ones integrating to become one (if you are a larger system).