[Pedro] met his son [Roberto] for dinner. Unfortunately [Pedro]'s son [Jeffrey] could not attend. [Dorothy]'s two sons, [James] and [Jeffrey] are both attending college in the fall.
('James', 'Roberto')
[Dorothy]'s two sons, [James] and [Jeffrey] are both attending college in the fall. [Pedro] met his son [Roberto] for dinner. Unfortunately [Pedro]'s son [Jeffrey] could not attend.
[{('James', 'brother', 'Roberto'): [('James', 'father', 'Pedro'), ('Pedro', 'son', 'Roberto')]}, {('James', 'father', 'Pedro'): [('James', 'brother', 'Jeffrey'), ('Jeffrey', 'father', 'Pedro')]}, {('James', 'brother', 'Jeffrey'): [('James', 'mother', 'Dorothy'), ('Dorothy', 'son', 'Jeffrey')]}]
['mother', 'son', 'father', 'son']