The article Magdlyn found was helpful! And I'm happy to explain my experience with Dissociative Identity Disorder (formerly multiple personality disorder) and answer any questions!
Pretty much, from the ages of birth to 9 years old, humans' personality states integrate into one personality. These states include simple things like how to act in order to recieve food, getting affection from caregivers, self soothing, etc. Sometimes, when a child has been through enough repeated trauma, these personality states don't fully integrate. Therefore, in my case, I'm essentially a bunch of people in a meatsuit. Each personality/alter/headmate with their own sets of memories, likes, mannerisms, names, genders, etc. The dissociation that causes these different alters means that what I have experienced as our Princess is not what Z has experienced. If our Princess was experiencing it, she was present in the body to some degree, and able to use it. This is called "fronting." I am my alters.
And literally all of these parts of myself are madly in love, as family as partners as parents and children. I'm literally an entire community in here, with some variation of amnesia between us. I have always been polyamorous with my headmates, in a very real sense of the word
