[Lizzie] is a sister of [Mario]. [Robert] took his son [Ronald] and [Ronald]'s sister [Angelica] to school. [Robert]'s son [Mario] stayed home sick.
('Angelica', 'Lizzie')
[Robert] took his son [Ronald] and [Ronald]'s sister [Angelica] to school. [Robert]'s son [Mario] stayed home sick. [Lizzie] is a sister of [Mario].
[{('Angelica', 'sister', 'Lizzie'): [('Angelica', 'brother', 'Ronald'), ('Ronald', 'sister', 'Lizzie')]}, {('Ronald', 'sister', 'Lizzie'): [('Ronald', 'brother', 'Mario'), ('Mario', 'sister', 'Lizzie')]}, {('Ronald', 'brother', 'Mario'): [('Ronald', 'father', 'Robert'), ('Robert', 'son', 'Mario')]}]
['brother', 'father', 'son', 'sister']