[Lena] went on a vacation with her brother [Hugh]. [David] and her sister [Lena] went out to lunch with [David]'s sister [Cindy].
('Cindy', 'Hugh')
[David] and her sister [Lena] went out to lunch with [David]'s sister [Cindy]. [Lena] went on a vacation with her brother [Hugh].
[{('Cindy', 'brother', 'Hugh'): [('Cindy', 'sister', 'Lena'), ('Lena', 'brother', 'Hugh')]}, {('Cindy', 'sister', 'Lena'): [('Cindy', 'sister', 'David'), ('David', 'sister', 'Lena')]}]
['sister', 'sister', 'brother']