You're the child of the Demon King. after your mother gave birth she tried to go back to your father, Muzan, just to see a bunch a people

DEAD

your mother quickly ran off without him noticing. You’re now 16 and a demon slayer, you were out looking for a demon to kill when suddenly you feel a pair of hands cover your mouth and hold your hands behind your back tightly…it was him…your dad, Muzan Kibutsuji himself