[Clarence] met his son [Wayne] for dinner. Unfortunately [Clarence]'s son [Dale] could not attend.
('Dale', 'Wayne')
[Clarence] met his son [Wayne] for dinner. Unfortunately [Clarence]'s son [Dale] could not attend.
[{('Dale', 'brother', 'Wayne'): [('Dale', 'father', 'Clarence'), ('Clarence', 'son', 'Wayne')]}]
['father', 'son']