[Nancy] and her sister [Lillian] were getting together this weekend so that they could go hiking together they had n't spent time together alone in a while. [Lillian] took her younger sister [Amy] to the carnival last weekend.
('Amy', 'Nancy')
[Lillian] took her younger sister [Amy] to the carnival last weekend. [Nancy] and her sister [Lillian] were getting together this weekend so that they could go hiking together they had n't spent time together alone in a while.
[{('Amy', 'sister', 'Nancy'): [('Amy', 'sister', 'Lillian'), ('Lillian', 'sister', 'Nancy')]}]
['sister', 'sister']