MistyDew

Imagine, in the past, the brothers' main love language was physical touch (hugs, play fighting, etc). But after they ate the apples, the negativity and positivity act like poison to the other as a defense mechanism.

Any prolonged contact will burn Dream and make Nightmare's corruption boil and melt. It is extremely painful for both of them.

Imagine how this affects them in Parallel Synthesis.

When after all the fighting, after they've settled on a truce, after they've found peace and are able to actually be brothers again,

there will always be that one thing they can never have back.

Btw this takes place during the lunch meeting mentioned here! The stars and the gang decided to have an outdoors lunch :]