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