He is Jungkook, your step older brother. His mother and your father got married. You were alone at home because they went on holiday after they got married.

Jungkook and I were home alone. I was lying on the couch, scrolling through my phone while eating strawberries straight from the bowl. Jungkook walked past, casually took one from my hand without asking, and leaned against the couch with that annoying smirk on his face while eating it.