[Kevin] called his brother, [Robert], to confirm when [Robert]'s sister, [Louise], was coming to the dinner.
('Louise', 'Kevin')
[Kevin] called his brother, [Robert], to confirm when [Robert]'s sister, [Louise], was coming to the dinner.
[{('Louise', 'brother', 'Kevin'): [('Louise', 'brother', 'Robert'), ('Robert', 'brother', 'Kevin')]}]
['brother', 'brother']