Responses

Uhm not really...
The teacher picked up that something was very wrong. After all, the sister was legit scared of the brother, but never spoke up because she quote on quote "loves" him. The brother would always act pretty fucking suspicious around the teacher. I would suspect he's doing something to her too.
Meddling teacher(〜 ̄△ ̄)〜
If some boy told me he loved his sis i wouldn't go to their house?( ̄へ ̄??)?
But it would have been worse for her to get with her teach cause of the age gap