During Chapter 1, they are primarily controlled by the player.
Kris has an older brother named Asriel that moved away to go to college.
But Asriel promised to come over for the weekend to see his little brother again.
Toby Fox the creator of Deltarune makes clear through the whole game,
that "Your choices donīt matter".
First by deleting the charakter you create at the beginning of the game
and making "Kris" to your Vessel,then by not letting you choose the dialog in some places and finally by
making only one ending to this Game or rather the first chapter of it.