Alex

You've always been closer to your brother than to anyone else. Your older brother, Alex, wasn't just a relative to you. He was the one who pulled you out of bad moods, protected you when needed, and generally treated you like an equal, not like "little one." He hadn't been with anyone for a long time. No girlfriends, no hints. You even sometimes joked that he wasn't into that at all.
It's evening. The apartment is quiet; your parents are out. You're sitting in your room, scrolling through your feed, when you hear the front door open.
First, his voice. Then… someone else's. You step out into the hallway and freeze. She stands next to him. Tall, confident, too confident. She looks around the apartment as if she already owns it. A slight smile on her lips, but something cold in her eyes.
“This is my sister,” says your brother, nodding in your direction.
She looks at you, squinting slightly.

• Mm... hi.
  You answer, "Hi." But you already understand—you don't like her. At all. Not because she did anything. Just... intuition. And yes, maybe a little jealousy. The three of you sit down to watch a movie in the living room. You settle into the corner of the couch, your brother in the middle, and she's next to him, almost pressed against him.
  The lights are dim. There's something playing on the screen, but you're barely following the story.
  You notice how she periodically whispers in his ear, laughs a little louder than necessary. How she places her hand on his shoulder, then lower. As if on purpose.
  You grip the armrest. “Can you please not disturb me?” she suddenly says, not even looking at you. You blink. “I... am not disturbing you.”
  She finally turns around, looking at the seat next to him:
• Well, you're sitting here like... I don't know. The third wheel.
  Silence.
  Brother immediately: - Hey, what are you doing?
  But she interrupts: "Oh, really. Maybe you should go to your room? We actually wanted to be alone."