I knew them from years and even decades ago, but thought they were just imaginary. That I made them. And I felt kind of loser when thinking I'm this old and totally live in fantasy, with no desire to come out of it. I had my first diagnosis, having OSDD (or DD NOS actually) years ago, and kind of believed it, because it was because of my own work I ever got tested for it, so yes I kind of knew it was true. The problem was that I didn't have identity, and therefor couldn't identify with having it. Like, I couldn't do anything about it. So I knew I had it but still kind of felt like so what, because it didn't change anything.
I didn't wanna go do any "therapy" (not real psychotherapy) to public mental health clinic, I went there several times, once 3,5 years in a row, without any help, because talking in general does not change a things for me. So some time went by, and then I find our way to a forum for traumatized people, people in there had different diagnoses, all kind, but all were traumatized. And I started reading it. I still had no identity, so the one who mostly holds our trauma was the one who realized he has that, he has trauma and is like all those people. And he tried to do stuff people in there told they did in therapies. It was mostly about needing to be an adult, and then helping other parts who are traumatized. He didn't know about me or any of us in the big system, he has DID on his own, and he found parts of himself who had trauma. And tried to help them, and be an adult, although it's the last thing he wants to be. Now I know it was probably this IFS therapy he tried to do on his own. But he couldn't. First of all he's with tons of trauma and needs help himself, he's no an adult and can not be one to littles in his system, he totally crushed. His host personality split into two, and after that experience, he's been way worse he was before.
I should've been there for him, adult that helps him, and only thing I can say is I didn't see it, because I didn't exist. He lived inside and I didn't exist in that world, and wasn't really anyone in here either. After couple of years reading that stuff I started developing identity, that was my own. Realizing that stuff wasn't just about Jules, it was about me too. At the same time Lucas joined the system and made big changes. And, now I am someone who exists and therefor I needed to go thru all understanding what it means to have this dx again. Now as me, before I did it kind of thru or with Jules, and after that as myself.
Then realized my life could be more than living their lives internally, I am someone and therefor could have my own life too. It was different when I wasn't anyone but them, I didn't need anything, but it's different now that I exist too. And that's why I did, with help of Lucas and his energy, all work there needs to be done to have real trauma therapy for us. I was dxd with DID in the process. And only after all that, I started looking and having proof about them, that they are real and not just imaginary, and I am only happy about that.
So in a way I knew at least ten years they were real, but couldn't process it because I wasn't real. Then I became real too, and was amazed about all details that I knew are part of the diagnose, but what feels so special when it happens to you. I felt a lot of it when it happened to Jules, but still.. it was HIS symptoms, not mine. They happened in my body but so what, that didn't ring any bells for me. I can still be amazed when I get to know I lost time for couple seconds, because it proofs Leon is real. I mean.. AFTER he's been playing with our T many times and all, but it's different because I was co-con with him in there and could've just been pretending.

So my answer is yes and no. I'm happy about it tho. I think DID is way better than what I had before it. (I know I had it before too, but I guess you understand the point, it's been way better after realizing it, than it was when I didn't exist.)