[Lillian] took her son [Douglas] to the park. [Douglas] and his brother [John] went to the arcade. They had a wonderful time.
('John', 'Lillian')
[Douglas] and his brother [John] went to the arcade. They had a wonderful time. [Lillian] took her son [Douglas] to the park.
[{('John', 'mother', 'Lillian'): [('John', 'brother', 'Douglas'), ('Douglas', 'mother', 'Lillian')]}]
['brother', 'mother']