[Douglas] asked his father [George] if they could go to the library. [George]'s father [Clarence] was there already, waiting for them.
('Douglas', 'Clarence')
[Douglas] asked his father [George] if they could go to the library. [George]'s father [Clarence] was there already, waiting for them.
[{('Douglas', 'grandfather', 'Clarence'): [('Douglas', 'father', 'George'), ('George', 'father', 'Clarence')]}]
['father', 'father']