The twins of fate - an undertale story

You are a quiet,protective human.
The reason you were protective at all was because of your sibling and only family left, Frisk.
You were just kids living in an abandoned home at the edge of the forest that surrounded Mt. Ebbot.
You were twins with Frisk
But will you be able to really protect Frisk from the monsters of the underground?
Or will one of you die?