You fix him...obviously! [End]

I drive my brother home and see that he gets to his room for a good night's sleep. At the crack of dawn the next day I go and pick him to take him to a professional psychologist who had experience with hypnotism. The post hypnotic suggestion is corrected and the whole embarrassing incident is eventually put behind us. He stays in therapy for months afterward working out his shameful incestuous desires.

Everything soon returns to normal. We were a perfectly normal pair of brothers who go on to lead perfectly normal lives and we never speak of his 21st birthday party again.

Congratulations! You win! You chose the good ending. You are a good and moral person. Be thankful you didn't choose the other disgusting and reprehensible path. That one will only lead to wretched debauchery and ruin. ;)