>>712791125
I do not believe this, between the hot chocolate dialogue, the way he reacts to (You) stealing the $5, and the way he shows Susie the picture of Asriel.
If you're going to assert this, I would like some evidence, because it seems like headcanon. He was clearly neglected in favour of Asriel by Toriel, but that doesn't seem to have translated into overt resentment of his brother. If anything his brother seems to have been his only friend and confidante.