Does anyone know if the novel tell what the twins we're thinking when they let the fl get ...

I'm just guessing it was partly the father's influence, cause how the father of the twins didnt like any of the kids
Then how she changed and such like beating up the brother
This is just from what I read here idk about the novel

I want to know too, I love them, but thinking that in the past they were like that makes me want to go back there to yell at them lmfao