Was Miriam raped as a child/young woman? That would partly explain the genesis of Jon's twisted take on sex, gender and sexuality. Miriam walks away from a rape understandably fucked up and never fully recovers psychologically. She then passes on some dark concept of human sexuality, born from trauma, to her mentally retarded son. It's a tale as old as time. She was probably crazy from birth but was driven to madness from a life of trauma, bad decisions, and disappointment. Add some shitty genetics and a man who's gay enough to blow a load in miriam and you have the monstrosity that is JY. The perfect specimen for a Halloween fright!