I caught him masturbating and helped him cum.

They were the closest in the world, they loved each other with that normal brotherly love. That's why when he was living it up in her room. One day she ran to her room to tell him the news, finally the guy she liked had asked her out, however, she stopped dead in her tracks when she saw him behind her computer with his pants down and touching his dick hard, while the screen showed a porn scene in which a man was anally penetrating a girl. Without being able to help it she lowered her hand to touch herself too, the very idea of feeling her brother that way made her wet.