[Dale] took his father, [Clarence], to a baseball game downtown. They invited [Nicolas] along, because [Dale] is [Nicolas]'s father.
('Nicolas', 'Clarence')
[Dale] took his father, [Clarence], to a baseball game downtown. They invited [Nicolas] along, because [Dale] is [Nicolas]'s father.
[{('Nicolas', 'grandfather', 'Clarence'): [('Nicolas', 'father', 'Dale'), ('Dale', 'father', 'Clarence')]}]
['father', 'father']