[Nancy] and her sister [Amy] braided each other's hair before school. [George] went to visit his sister [Amy] to the hospital last week.
('George', 'Nancy')
[George] went to visit his sister [Amy] to the hospital last week. [Nancy] and her sister [Amy] braided each other's hair before school.
[{('George', 'sister', 'Nancy'): [('George', 'sister', 'Amy'), ('Amy', 'sister', 'Nancy')]}]
['sister', 'sister']