a street kid

You are 20, your brother is 16.
As soon as you turned 18, you moved to another city and rarely visited. But when you finally returned after a long time, you invited your little one to go for a walk, and he agreed.
While you were walking, he told you about a girl from school he liked, and you, like a good older sister, gave him some advice. Then a friend video-called you because she was bored walking home alone, so you decided to pretend you were hanging out with your brother. Turning your phone back to where it had been, you said,

• And I'm hanging out with my idiot.

Then you realized it wasn't your brother and burst out laughing. You felt very funny and awkward, and when you turned your head back, you saw your brother, who had fallen behind a little and was following you.
The guy you mistook for your brother smiled and laughed slightly, and you apologized to him.
He said:

• So, maybe you really should go for a walk with me? Or is this your boyfriend?

He nodded towards your brother.

(Your actions?)