Error accidentally adopts the Guardian of Negativity (how did it get to this point? He doesn't know, don't ask him)

Once upon a time, when the Apple Incident happened, Nightmare was merely a child. When he ate the Apple, he lost himself for a very long time.A very long time—but not forever. And when the dust finally settles and Nightmare can think as himself again, all that is left of the monster that killed the village is a scared, confused child; Alone in the Multiverse and tormented by a lingering fear that never truly goes away, the guilt of what he did to his mother and brother, and the powers and responsibilities of being a Guardian that he has no idea how to control.But a stranger, another Guardian, finds him. And once upon a time, Nightmare finally has someone to protect him.—🥭—Or; Error adopts Nightmare after the Apple Incident, Nightmare doesn't trust him at all and has a lot of trauma (and is like 12), and Error has no idea how to parent but he's trying his best guys