Complex sentence: Her claim to the House of Kawānanakoa would probably pass to her first-cousin-once removed, Prince Quentin Kawānanakoa, although she has an adopted son, David Kalakaua Kawananakoa, who might succeed her instead.
Split into simpler sentences: Her claim to the House of Kawānanakoa would probably pass to her first-cousin-once removed, Prince Quentin Kawānanakoa. But, she has an adopted son, David Kalakaua Kawananakoa, who would probably succeed her instead.