[Milton] asked his son, [Nicholas], to help paint his house. [Nicholas] asked his father, [Clarence] to help him build a birdhouse.
('Clarence', 'Milton')
[Nicholas] asked his father, [Clarence] to help him build a birdhouse. [Milton] asked his son, [Nicholas], to help paint his house.
[{('Clarence', 'grandson', 'Milton'): [('Clarence', 'son', 'Nicholas'), ('Nicholas', 'son', 'Milton')]}]
['son', 'son']