[Clarence] helped his grandson [Robert] cut the lawn for [Robert]'s mother, [Nancy].
('Nancy', 'Clarence')
[Clarence] helped his grandson [Robert] cut the lawn for [Robert]'s mother, [Nancy].
[{('Nancy', 'father', 'Clarence'): [('Nancy', 'son', 'Robert'), ('Robert', 'grandfather', 'Clarence')]}]
['son', 'grandfather']