You are Reki's sister/brother

You're Reki's sister/brother, and yours are one year apart—he's older than you. You don't have any friends in your class, but since you have a sister who's a year younger than you and twin sisters who are three, you don't really need friends. You are sitting at the table (you are having a family dinner). At the family dinner are Koyom (she is a year younger than you), Reki, Grandma, Mom, Nanaka and Chihiro (the sister of the twins who are 3 years old).