[Robert] bought a book for his father [Harold]. [Robert] played tennis with his sisters [Beverly] and [Tracy]. [Beverly]'s son [Samuel] skateboarded instead.
('Harold', 'Samuel')
[Robert] bought a book for his father [Harold]. [Robert] played tennis with his sisters [Beverly] and [Tracy]. [Beverly]'s son [Samuel] skateboarded instead.
[{('Harold', 'grandson', 'Samuel'): [('Harold', 'daughter', 'Beverly'), ('Beverly', 'son', 'Samuel')]}, {('Harold', 'daughter', 'Beverly'): [('Harold', 'son', 'Robert'), ('Robert', 'sister', 'Beverly')]}, {('Robert', 'sister', 'Beverly'): [('Robert', 'sister', 'Tracy'), ('Tracy', 'sister', 'Beverly')]}]
['son', 'sister', 'sister', 'son']