[Nicholas] was so proud that his son [Dennis] won the science fair! [Nicholas] bought a book for his father [Clarence].
('Clarence', 'Dennis')
[Nicholas] bought a book for his father [Clarence]. [Nicholas] was so proud that his son [Dennis] won the science fair!
[{('Clarence', 'grandson', 'Dennis'): [('Clarence', 'son', 'Nicholas'), ('Nicholas', 'son', 'Dennis')]}]
['son', 'son']