[Nancy]'s son [Robert] is running for class president. [Robert]'s sister [Linda] is helping make signs.
('Nancy', 'Linda')
[Nancy]'s son [Robert] is running for class president. [Robert]'s sister [Linda] is helping make signs.
[{('Nancy', 'daughter', 'Linda'): [('Nancy', 'son', 'Robert'), ('Robert', 'sister', 'Linda')]}]
['son', 'sister']