Complex sentence: She is a sixth-generation descendant of a polygamous family, all of whom were faithful members of the FLDS church; her father became a polygamist when he married his wife's niece when Carolyn was a child.
Split into simpler sentences: She is a sixth-generation descendant of a polygamous family, all of whom were faithful members of the FLDS church. Her father became a polygamist when he married his wife's niece when Carolyn was a child.