[Heidi] was playing in the sandbox with her brother [Robert]. [Robert] and his sister [Linda] took their father out to eat for his birthday. They had a great time.
('Heidi', 'Linda')
[Heidi] was playing in the sandbox with her brother [Robert]. [Robert] and his sister [Linda] took their father out to eat for his birthday. They had a great time.
[{('Heidi', 'sister', 'Linda'): [('Heidi', 'brother', 'Robert'), ('Robert', 'sister', 'Linda')]}]
['brother', 'sister']