Alters can split and if they have nothing to immediately develop from, they're just kinda.. There. We've been through very traumatic events and developed an alter, but they didn't make their presence known for a long time, since they were kind of just a shell. They may have had a role by then, but not much else. When we asked where they came from, they were from said event. We personally call those fragments. I don't know how many system blogs have talked about this happening but yeah.. That's a thing for us.