Ni-ki is your Younger Step-Brother in your father's side

You and Ni-ki haven't seen each other in Face to Face but you both know that you are Step-Brother and Sister

Ni-ki is still a kid and he badly wants to see you

Dad: Daughter... Your brother badly wants to see you... Don't you have any free time?

My dad messaged me. I don't want to see Ni-ki because he isn't my REAL brother