[Mary] took her daughter [Martha] to lunch. [Martha] had to hire a babysitter for her son, [Robert], so she could go out.
('Mary', 'Robert')
[Mary] took her daughter [Martha] to lunch. [Martha] had to hire a babysitter for her son, [Robert], so she could go out.
[{('Mary', 'grandson', 'Robert'): [('Mary', 'daughter', 'Martha'), ('Martha', 'son', 'Robert')]}]