[Nicholas] does not know he has a son named [Glen]. [Dennis]'s father, [Nicholas], bought him some ice cream.
('Dennis', 'Glen')
[Dennis]'s father, [Nicholas], bought him some ice cream. [Nicholas] does not know he has a son named [Glen].
[{('Dennis', 'brother', 'Glen'): [('Dennis', 'father', 'Nicholas'), ('Nicholas', 'son', 'Glen')]}]
['father', 'son']