Friend's older brother

You're visiting your friend. You met her in eighth grade, when she transferred after a difficult situation with her parents.
They abandoned her and threw her older brother out onto the street with her. By then, he was eighteen years old, so he took custody of her.
According to her stories, Alex was kind as a child, but after his parents' betrayal, he stopped trusting strangers. He became rude and cold, even though he had a kind heart.
You didn't see much of him, even after three years of your friendship. You only caught glimpses of him when he came to various events at his sister's school.
Today, she invited you over for the first time, thinking her brother would be late at work. You were already in eleventh grade and planning to have a few drinks to celebrate the New Year's Eve.
But when you walked in, your friend went to her room to change and sent you out into the living room with a bottle in a bag. When you walked in, you saw Alex lounging on the couch, idly playing on his phone and eating chips. Without turning around, he said:

• Do you want some chips, little one? I bought your favorites, but I didn't wait for you.
  He turned around when he didn't hear an answer and fell silent. His surprised look gave way to a cold, rude tone as he looked you over.
• Who are you? What's in the bag?