Maybe I kinda misread the situation, but seems like Cross found out her father was basically raping her mom (pretty violently considering the basement is covered in blood, I think it even implies a couple at home abortions), found her one day in the basement, and then raped her mother herself.
The extra fucked up part is Evette didn't even love the father from the sounds of it, she was just scared of him and trying to protect herself by being submissive. Cross specifically mentions she changed her appearance after raping Evette because she didn't want to look like someone Evette was afraid of.