Not me.
Whenever the parents and the siblings are offed by the BF, the girl is the one who is driving the truck. Not every time, but almost.
Killing the fam (of the girlfriend) is a Juliet fantasy, not a Romeo one.
Don't get me wrong, the boy or man is guilty of his crime, and deserves to die.
But any man who has not been temporarily insane over a woman really can't understand the root of a crime like this.
It sounds more and more like she consciously played him.
And though that is no justification for the crime-of course, he must have loved it... and he is certainly to blame.
The young lady here, has some culpability in the death of her mother and brother, because it looks like she could have interfered with HIS plans, but didn't. In some way, to some extent, he was satisfying SOME part of her agenda... bank on it.