[Pamela] does n't like her brother [Charles]. [Chris] hit his brother [Charles] in the head. [Chris] and his sister [Martha] went to the park.
('Pamela', 'Martha')
[Pamela] does n't like her brother [Charles]. [Chris] hit his brother [Charles] in the head. [Chris] and his sister [Martha] went to the park.
[{('Pamela', 'sister', 'Martha'): [('Pamela', 'brother', 'Chris'), ('Chris', 'sister', 'Martha')]}, {('Pamela', 'brother', 'Chris'): [('Pamela', 'brother', 'Charles'), ('Charles', 'brother', 'Chris')]}]
['brother', 'brother', 'sister']