[Tracy] is best friends with her sister [Dorothy]. [Dorothy] does not get along with her brother [Louis]. [Robert] went skiing with his brother [Antonio]. [Antonio]'s sister [Dorothy] watched from the ski lodge.
('Louis', 'Robert')
[Tracy] is best friends with her sister [Dorothy]. [Dorothy] does not get along with her brother [Louis]. [Robert] went skiing with his brother [Antonio]. [Antonio]'s sister [Dorothy] watched from the ski lodge.
[{('Louis', 'brother', 'Robert'): [('Louis', 'sister', 'Dorothy'), ('Dorothy', 'brother', 'Robert')]}, {('Dorothy', 'brother', 'Robert'): [('Dorothy', 'brother', 'Antonio'), ('Antonio', 'brother', 'Robert')]}, {('Louis', 'sister', 'Dorothy'): [('Louis', 'sister', 'Tracy'), ('Tracy', 'sister', 'Dorothy')]}]
['sister', 'sister', 'brother', 'brother']