Complex sentence: Chihaya has a tragic past due to the death of her younger brother in a car accident eight years ago, which she blames herself for and also lead to her parents divorcing and driven a wedge between her and her parents.
Split into simpler sentences: Chihaya has a troubled past due to the death of her younger brother in a car accident eight years ago, which she blames herself for. Her brother's death also lead to her parents divorcing and driven a wedge between her and her parents.