Fiction similar to v.c. andrews

Weird horror type book written in similar style to V.C. Andrews. I remember that the family had 1 son and 3 daughters. The mom killed the husband and buried him in the yard (I think that was on the cover with a daughter watching out a window). The nanny walked in on the boy naked in the tub with 2 of his sisters. He had the nanny's crucifix on his penis and the girls are trying to catch it in their mouths. She runs away and he throws it at her and she falls down the stairs and dies. The oldest daughter runs away. She comes back many years later out of guilt. They gave her the mothers "tea" that knocks her out. She wakes up with a shaved head and bruises I think. She hides from her fiancé. I think the book ended with the brother bringing a fish home for them to cook that had a blue bubble in it. He dies and the sister lays down next to him and dies as well. I don't remember much else about it other than it was a really weird book.