Complex sentence: When Kain was a boy his mother found herself engaged to Sabato Rokudo, Rinne's father, who constantly borrowed money from her, thereby leaving her and her son to live on the verge of bankruptcy.
Split into simpler sentences: When Kain was a boy his mother found herself engaged to Sabato Rokudo. The father of Rinne constantly borrowed money from her, leaving her and her son to live on the verge of bankruptcy.