[Amy] is taking a trip to see her sister [Nancy]. [George] always enjoyed playing with his sister, [Amy], when they were growing up.
('George', 'Nancy')
[George] always enjoyed playing with his sister, [Amy], when they were growing up. [Amy] is taking a trip to see her sister [Nancy].
[{('George', 'sister', 'Nancy'): [('George', 'sister', 'Amy'), ('Amy', 'sister', 'Nancy')]}]
['sister', 'sister']