And there's reincarnation.
Because Dasaroi are psychic, they're a lot more aware of their past lives than a baseline human would be. It's not a hazy thing that you need a therapist's regression for. It's there for you to access; essentially, all you have to do is ask your brain for the info.
To use a silly analogy - Kieran would be the OS of his system, as he's the current living person. Let's say Airenn is iTunes, Teague is Firefox, etc. - double-click with intent, and it's all right there.
The kids who grow up knowing what they are are trained from an early age how to keep that compartmentalized - which is mostly is on its own, but there can be inadvertent bleedover, and essentially they just need to be able to figure out that that's not their thought of sense-memory, and tuck it back where it goes.
Kids who don't know what they are - like Napalm, Julia, Lyric - are going to have more than a few problems with this. Julia's mostly come out in her dreams. Lyric's... Lyric (who has MPD) was broken so early in life that she never learned how to consciously separate, so past Lyrics have moved in, so to speak. Lyric and Lily are both new to this lifetime, but not everyone in that body is. Some of them are those past lives, who sometimes don't even know that they're past lives. Lyric's OS is b0rked. Julia's is just slightly fragmented - her personality is whole, so once she knows that yes, the dreams are real, and that's where they come from, she's able to tuck them all away.
They're born with this. With other lives in their heads.
When you get someone else in your head as an adult, it can be horribly disorienting. My example on this is Halloran, during the Purges, when his brother - the Kithrayn - died, and his mind & spirit slammed into Halloran, making him Kithrayn. Highly unusual, that. So Halloran has a bit of a problem sorting Michael-thoughts from Halloran-thoughts for a little while. After his mind separates from Capri's. Heh. Yeah. Bad year or so for Halloran in regards to knowing where his thoughts come from, on top of everything else...