[Nicholas] and his son [Dennis] went to the park and saw [Nicholas]'s father [Clarence] there with his dog.
('Dennis', 'Clarence')
[Nicholas] and his son [Dennis] went to the park and saw [Nicholas]'s father [Clarence] there with his dog.
[{('Dennis', 'grandfather', 'Clarence'): [('Dennis', 'father', 'Nicholas'), ('Nicholas', 'father', 'Clarence')]}]
['father', 'father']