[Hugh] and her sister [Cindy] decided to take a trip to Mexico together. [Joshua] invited his sister [Lena] to dinner. [Joshua]'s brother [Hugh] was too busy to attend.
('Cindy', 'Lena')
[Hugh] and her sister [Cindy] decided to take a trip to Mexico together. [Joshua] invited his sister [Lena] to dinner. [Joshua]'s brother [Hugh] was too busy to attend.
[{('Cindy', 'sister', 'Lena'): [('Cindy', 'brother', 'Joshua'), ('Joshua', 'sister', 'Lena')]}, {('Cindy', 'brother', 'Joshua'): [('Cindy', 'brother', 'Hugh'), ('Hugh', 'brother', 'Joshua')]}]
['brother', 'brother', 'sister']