story: [Edward] asked his father, [Preston], to help him with his math homework. [Preston] could n't, because he was lousy at math himself. [Brian] went to the park with his father, [Preston]. [Mack]'s father [Preston] is going to coach the team this year.
query: ('Edward', 'Mack')
clean_story: [Edward] asked his father, [Preston], to help him with his math homework. [Preston] could n't, because he was lousy at math himself. [Mack]'s father [Preston] is going to coach the team this year.
proof_state: [{('Edward', 'brother', 'Mack'): [('Edward', 'father', 'Preston'), ('Preston', 'son', 'Mack')]}]