[Heidi] and her sister [Lorraine] went to the basketball game. [Heidi] invited [Kevin] to meet them there, since she is his sister.
('Kevin', 'Lorraine')
[Heidi] and her sister [Lorraine] went to the basketball game. [Heidi] invited [Kevin] to meet them there, since she is his sister.
[{('Kevin', 'sister', 'Lorraine'): [('Kevin', 'sister', 'Heidi'), ('Heidi', 'sister', 'Lorraine')]}]
['sister', 'sister']