[Cheryl] is getting married. She is looking forward to her sister, [Annie], attending. They have n't seen each other since [Annie] relocated to California with her husband 3 years ago. [Rebecca] called [Annie], her sister, to see if she wanted to go out to eat. [Rebecca] took her younger sister [Heather] to the carnival last weekend. [Heather] was sewing a sweater for her sister [Rebecca].
('Cheryl', 'Rebecca')
[Cheryl] is getting married. She is looking forward to her sister, [Annie], attending. They have n't seen each other since [Annie] relocated to California with her husband 3 years ago. [Rebecca] called [Annie], her sister, to see if she wanted to go out to eat. [Heather] was sewing a sweater for her sister [Rebecca]. [Rebecca] took her younger sister [Heather] to the carnival last weekend.
[{('Cheryl', 'sister', 'Rebecca'): [('Cheryl', 'sister', 'Heather'), ('Heather', 'sister', 'Rebecca')]}, {('Cheryl', 'sister', 'Heather'): [('Cheryl', 'sister', 'Annie'), ('Annie', 'sister', 'Heather')]}, {('Annie', 'sister', 'Heather'): [('Annie', 'sister', 'Rebecca'), ('Rebecca', 'sister', 'Heather')]}]
['sister', 'sister', 'sister', 'sister']