[Theresa] is taking a trip to see her sister [Lillian]. [Theresa] took her younger sister [Amy] to the carnival last weekend.
('Amy', 'Lillian')
[Theresa] took her younger sister [Amy] to the carnival last weekend. [Theresa] is taking a trip to see her sister [Lillian].
[{('Amy', 'sister', 'Lillian'): [('Amy', 'sister', 'Theresa'), ('Theresa', 'sister', 'Lillian')]}]
['sister', 'sister']