[Marie] cooked her son [Allan] his favorite meal yesterday because it was his birthday. [Mario] and his brother [Ronald] are looking for a good gift for [Ronald]'s mother [Marie]. [Allan] bought a book for his father [Robert].
('Robert', 'Mario')
[Allan] bought a book for his father [Robert]. [Marie] cooked her son [Allan] his favorite meal yesterday because it was his birthday. [Mario] and his brother [Ronald] are looking for a good gift for [Ronald]'s mother [Marie].
[{('Robert', 'son', 'Mario'): [('Robert', 'son', 'Allan'), ('Allan', 'brother', 'Mario')]}, {('Allan', 'brother', 'Mario'): [('Allan', 'brother', 'Ronald'), ('Ronald', 'brother', 'Mario')]}, {('Allan', 'brother', 'Ronald'): [('Allan', 'mother', 'Marie'), ('Marie', 'son', 'Ronald')]}]
['son', 'mother', 'son', 'brother']