Complex sentence: His mother, whose maiden name was Lydia Brown, was a descendant of Robert Barclay of the Barclay clan who was a governor of the East Jersey colony in North America in the 1680s.
Split into simpler sentences: His mother, whose maiden name was Lydia Brown, was a descendant of Robert Barclay of the Barclay clan. Barclay was a governor of the East Jersey colony in North America in the 1680s.