Jujitsu Kaisen x SukunaSibling!Child!reader

Your backstory

D**th ⚠️

It was a sunny day, 8 year old Sukuna was studying books on curses.
"Sukuna, come here, please!" His father yelled across the palace.
"Coming, otou-san!" He yelled back, making sure to mark where he left off. He hurriedly went to the bedroom where his father called him.
"Yes, otou-san?" He huffed. His father smiled at him and asked, "Would you like to see your baby sibling?" Sukuna froze. Baby? Sibling? He looked at his father and mindlessly nodded. The door opened to reveal his mother holding a bundle of blankets. She motioned for him to come see.
Your eyes were red, like blood. Your hair, barely grown in, was the same as Sukuna's. You look at Sukuna and babble at him. His face was full of wonder. Your hands reach around his finger. You start cooing and giggling, spit coming out involuntarily. Sukuna smiles as he's handed the bundle.
"Look at you, little blossom. You're going to be powerful one day, I can feel it. I promise to stick by you to teach you everything I know. I will comfort you when you're hurt and will laugh when you are happy. I'll be the best brother you'll ever have. I promise." He says before kissing your forehead softly and bobbing you softly. You fall asleep in his arms, and your hand still holds him. He couldn't get happier than this.