story: [Preston] went to the beach with his sister [Nancy] and his daughter [Karen]. [Crystal] and her sister [Nancy] are the only children in their family.
query: ('Nancy', 'Karen')
clean_story: [Preston] went to the beach with his sister [Nancy] and his daughter [Karen].
proof_state: [{('Nancy', 'niece', 'Karen'): [('Nancy', 'brother', 'Preston'), ('Preston', 'daughter', 'Karen')]}]