story: [Otto] and his sister [Nancy] were twins. Still, they did n't look very much alike. [Otto]'s sister, [Crystal], bought movie tickets at a discount rate. [Crystal] has a son called [David]. Each day they go to the park after school.
query: ('Otto', 'David')
clean_story: [Otto]'s sister, [Crystal], bought movie tickets at a discount rate. [Crystal] has a son called [David]. Each day they go to the park after school.
proof_state: [{('Otto', 'nephew', 'David'): [('Otto', 'sister', 'Crystal'), ('Crystal', 'son', 'David')]}]