[John] and his brother [Douglas] were rarely seen apart. [Ann] took her brother [Douglas] to work Monday because his car was in the shop getting a tune up.
('John', 'Ann')
[John] and his brother [Douglas] were rarely seen apart. [Ann] took her brother [Douglas] to work Monday because his car was in the shop getting a tune up.
[{('John', 'sister', 'Ann'): [('John', 'brother', 'Douglas'), ('Douglas', 'sister', 'Ann')]}]
['brother', 'sister']