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