[Michael] asked his sister [Emily] to help him with his math homework. [Emily] was n't sure what to do, so she asked her sister [Mary] for some help.
('Mary', 'Michael')
[Michael] asked his sister [Emily] to help him with his math homework. [Emily] was n't sure what to do, so she asked her sister [Mary] for some help.
[{('Mary', 'brother', 'Michael'): [('Mary', 'sister', 'Emily'), ('Emily', 'brother', 'Michael')]}]
['sister', 'brother']