What's going on between Brody and Cassie ???

I jut saw Episode 2 of Season 4 and I don't know if anda noticed (or maybe I am completely paranoid and blinded oleh Brody Weston's sexiness...) but there is something going on between the junior and the teacher. Did anda notice that ? What do anda thing it is ? Did they dated ? Are they brother and sister ? Anything else ?

NB : It felt good to see Puck talk to Jake !