Anti: "A... a noise."

Annie finds some curtains.  Curious, she peeks behind them and sees two small skeletons, one slightly bigger than the other.
Annie: "Oh...!"
The two skeletons look at her.  The shorter seems wary.  The taller waves happily.
Annie: "Hello...there is no need to be afraid.  I won't hurt you.  What are your names?"
The shorter one still seems wary, but relaxes slightly.
???: "S-ans."
It points to the taller.
Sans: "Pa-py... Pa-py-rus."
Annie: "Sans and Papyrus?  Those are nice names.  My name is-"

Anti: "...Sans...and...Papyrus... ..."
Frisk: "...you DO know them?"
Anti: "... I..."

A/N: Hoooooo boy, this is fun.  By the way, this is based off of my headcanon that the skelebros were more of Gaster's experiments, but later on became more like sons to him.