One common things among people with MPD, are their personalities conflicting, and fighting. It could be a general distaste for the other persona, or a fight over certain thing. If they just have a general hatred for each other, it may die down with time, but more than likely stay that way for ever. Two of my personalities, Raven and Luci, have always hated each other. They are both very dominant personalities, and very polar opposite. Another person I know with MPD only has one other personality, and they have a general hatred for one another as well. Rarely do they ever agree with something. If you don’t help the fighting, it can be very counter productive, and damaging to your personal life. I’ve noticed this is a very common issue, and what has helped is trying to provide an understanding of one another. For this to happen, you could say, write a journal to each other, one entry a day. You could also take up hobbies, find things you’re passionate about. Learn about one another. Form respect for each other.
It can take years for this to happen, but as it happens, life gets more simple, and smoother for everyone. Patience is the key to this, and wanting to understand yourself, as a whole.