It is taboo to sleep with your cousin
Susie is attending a big family reunion and having a few drinks.
Susie wants to have sex with someone.
Susie chats with one of the catering crew and goes home with him when he's finished working.
Susie invites her first cousin to come home with her for carnal relations.
Susie has a fun evening enjoying sex with her new found friend.
Susie is blackballed by her family when they hear about her incestuous behavior.