Because children's brains are still developing, they may perceive things differently than us adults. With DID, our parts are often different ages with different personalities, so they will also likely perceive things differently than us, the host persons. Just because perceptions are different, however, it doesn't mean that anyone is lying or untrustworthy. It simply means that they see it from a different angle than we do. And, sometimes our alters dissociate themselves. For those who don't have DID, they recall things in accordance with the age they experience trauma, and they sometimes "fill in the blanks" with things that don't make sense as adults retrospectively looking back but did make sense to their younger self that experienced it. --This may be a lot to absorb, but it is helpful for your understanding your different parts and different perceptions, as well as being willing to communicate with them and believe them or at least the pain they are expressing, whether it be through memories, words, dreams, or nightmares. Our parts are telling us their pain, and it is good to hear them, comfort them and yourself, and share these things with a trustworthy therapist who is competent and trained to help you and your alters.

I'm sure your therapist or some other literature out there regarding autobiographical memory, traumatic memory, cognition, and development can help you with some of the more scientific answers to this, which remain debatable and somewhat controversial.

For your peace of mind, however, it is enough to know existentially what it is you're feeling, perceiving, and experiencing within yourself (or in this case, your selves), and to accept all parts of yourself in a kind, caring way. I hope this helps.