[Douglas] went to dinner with his grandfather, [Clarence]. [Douglas] was upset that his brother, [John], could n't be at the dinner.
('John', 'Clarence')
[Douglas] went to dinner with his grandfather, [Clarence]. [Douglas] was upset that his brother, [John], could n't be at the dinner.
[{('John', 'grandfather', 'Clarence'): [('John', 'brother', 'Douglas'), ('Douglas', 'grandfather', 'Clarence')]}]
['brother', 'grandfather']