[Marie]'s husband [Robert] and son [Mario] went on a ski trip with [Mario]'s brother, [Ronald]. [Pedro] and his brother [Robert] were rarely seen apart.
('Pedro', 'Ronald')
[Pedro] and his brother [Robert] were rarely seen apart. [Marie]'s husband [Robert] and son [Mario] went on a ski trip with [Mario]'s brother, [Ronald].
[{('Pedro', 'nephew', 'Ronald'): [('Pedro', 'brother', 'Robert'), ('Robert', 'son', 'Ronald')]}, {('Robert', 'son', 'Ronald'): [('Robert', 'wife', 'Marie'), ('Marie', 'son', 'Ronald')]}, {('Marie', 'son', 'Ronald'): [('Marie', 'son', 'Mario'), ('Mario', 'brother', 'Ronald')]}]
['brother', 'wife', 'son', 'brother']