Complex sentence: Petar's wife (Katarina Zrinska) and two of their daughters died in convents, and his son, Ivan, died mad after a terrible imprisonment and torture as did Katarina, the very symbol of Croatia's destiny.
Split into simpler sentences: Petar's wife (Katarina Zrinska) and two of their daughters died in convents, and his son Ivan, died mad after a terrible imprisonment and torture. So did Katarina, the very symbol of Croatia's destiny.