Complex sentence: Paravicini is the son of Nicolas Paravicini and Mary Ann Parker Bowles, sister of Andrew Parker Bowles and thus the former sister-in-law of Camilla, who later, by her marriage to the Prince of Wales, became Duchess of Cornwall.
Split into simpler sentences: Paravicini is the son of Nicolas Paravicini and Mary Ann Parker Bowles, sister of Andrew Parker Bowles. Paravicini's aunt (by marriage) was Camilla, who later, by her marriage to the Prince of Wales, became Duchess of Cornwall.