[Pedro] called his brother [Louis] on Friday because it was his birthday. [Pedro] and his brother [Robert] are fighting again. [Dorothy] went to the party with her brother [Robert] and her sister [Tracy].
('Tracy', 'Louis')
[Dorothy] went to the party with her brother [Robert] and her sister [Tracy]. [Pedro] and his brother [Robert] are fighting again. [Pedro] called his brother [Louis] on Friday because it was his birthday.
[{('Tracy', 'brother', 'Louis'): [('Tracy', 'brother', 'Pedro'), ('Pedro', 'brother', 'Louis')]}, {('Tracy', 'brother', 'Pedro'): [('Tracy', 'brother', 'Robert'), ('Robert', 'brother', 'Pedro')]}, {('Tracy', 'brother', 'Robert'): [('Tracy', 'sister', 'Dorothy'), ('Dorothy', 'brother', 'Robert')]}]
['sister', 'brother', 'brother', 'brother']