That siblings have sex together?

And how did Kate die, was it really car accident? I know he found her in car, but it wasn't clear to me if she really died because of car accident or if his brother killed her. Kangaroo accident is from present when Ned was driving car with his GF, not from past.

Btw. Sophie Lowe looks great, but movie was just average, maybe only one touching (final) scene, didn't like soundtrack, liked nudity, otherwise boring.