Apparently, Dion never killed fl's brother (he does but her brother lives). What he feels for fl is not love but obsession and I just blame it on the father for his personality. His emotions (human self) were taken away by his father. Thus, feeling emotionless as a child until he saw fl cry. That's why he supper obsessed with making her cry, he wants to feel the emotion (feel human) again that he lost. Dion's character is quite sad, he wants to be free from the house too. He and Jeremy will be the only sibling alive other than fl. After he is free, he wanders. He realizes he's badly twisted/broken and now he's free. He struggles to find a place for himself.
Dion's character (spoiler)
Apparently, Dion never killed fl's brother (he does but her brother lives). What he feels for fl is not love but obsession and I just blame it on the father for his personality. His emotions (human self) were taken away by his father. Thus, feeling emotionless as a child until he saw fl cry. That's why he supper obsessed with making her cry, he wants to feel the emotion (feel human) again that he lost. Dion's character is quite sad, he wants to be free from the house too. He and Jeremy will be the only sibling alive other than fl. After he is free, he wanders. He realizes he's badly twisted/broken and now he's free. He struggles to find a place for himself.
Seriously, he needs someone too!