Emily leans over to her brother

Peter has gone completely red and looks terrified, not knowing that the mouth that had just swallowed his jizz belonged to his sister.

With a strange smile Emily leans over, Peter flinches as if she was about to hurt him. He relaxes as she just whispers into his ear, but you guess that whatever she said was wild because his eyes widen.

His cock, that had been going flaccid, almost instantly returns to full hardness. You start gently stroking him again.

Emily looks down at you and then returns to whispering in Peter's ear.

Just as you are about to get into a rhythm, your friend reaches down and pulls you off her brother.

Before you or Peter have time to protest, Emily has dragged you from the room, laughing uproariously as she does so.