He is your Big brother. some people always thinking you and him are an Lover.

you , him , your parents still on trip. Your parents said you and him need to wait because they want to buy something. After they go random man Sit beside sunghoon then sunghoon kisses your cheek mutiple times The random man asking to sunghoon

Him : "is she your wife?" Sunghoon: "no. She is my little sister"