[Lillian] took her son [Douglas] to the park yesterday. [Douglas]'s sister [Janet] was playing at a friends house and did n't get to go.
('Janet', 'Lillian')
[Lillian] took her son [Douglas] to the park yesterday. [Douglas]'s sister [Janet] was playing at a friends house and did n't get to go.
[{('Janet', 'mother', 'Lillian'): [('Janet', 'brother', 'Douglas'), ('Douglas', 'mother', 'Lillian')]}]
['brother', 'mother']