(Gaster was the father of Sans and Papyrus and you, the adopted one)

Gaster, the father, just looked at you with his permanent smile as he had his hands folded behind his back.

Sans stood next to Papyrus, silently staring at you. He had his hands in his pockets as he had a toothy-wide grin on his face. Yet, he didn't looked happy or excited at all.

Papyrus on the other hand looked pretty excited and happy to have a new sibling, even if its adopted. He looked down at you, smiling widely.