So... nm hates his brother... but will also risk his life to keep a small part of him alive.... but also hates him completely? What kind of relationship does he want with dream??
Both have a warped and corrupted view of each other. Nm is the one whose corruption is the most obvious, taking the worst of it with all the apples. Dream, too, is corrupted in a sense, imagine the apple gives them a singleminded focus to force positivity onto the multiverse, to rid it of all negativity (maybe so Nm would come back?). The poor apple is overcompensating.
Nm truly thinks the dreamling is actually the last part of their sibling that’s alive. They view Dream as an impostor, a hollow apparition meant to mock them with their “I will find a way to save you” or “If you are there, somewhere, I will get rid of the poison that is within you now.” But that just can’t be. That thing is gone. They are back, no? They surely won back then.
All Dream sees is the corruption, not knowing that Nm is still there, if barely. They hate that thing that has caused them all trouble for far too long. But Dream knows there must be a way to bring Nm back, somewhere, without purgin all negativity of the multiverse (they still got some sense...).
You can think of this concept as them both being, in a sense, in disarray. They have no balance between them because they weren’t made for the roles they now have, just to guard, not to balance. This was forced upon them out of sheer desperation. So both can easily tilt into a rather black and white worldview.
But honestly? Lol, I’m no storyteller. Any amateurish inconsistencies are because I know shit and I am a fool playing around with concepts I like. Im learning as I go jajaja