[Nicholas] went with his sister [Nancy] to get groceries and [Nancy]'s sister [Theresa] went with them.
('Theresa', 'Nicholas')
[Nicholas] went with his sister [Nancy] to get groceries and [Nancy]'s sister [Theresa] went with them.
[{('Theresa', 'brother', 'Nicholas'): [('Theresa', 'sister', 'Nancy'), ('Nancy', 'brother', 'Nicholas')]}]
['sister', 'brother']