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