[David] took her sister [Lynn] out for dinner to celebrate her birthday. [David] took her son [Bobby] to school and his grandfather [James] picked him up at then end of the school day.
('Lynn', 'James')
[David] took her sister [Lynn] out for dinner to celebrate her birthday. [David] took her son [Bobby] to school and his grandfather [James] picked him up at then end of the school day.
[{('Lynn', 'father', 'James'): [('Lynn', 'sister', 'David'), ('David', 'father', 'James')]}, {('David', 'father', 'James'): [('David', 'son', 'Bobby'), ('Bobby', 'grandfather', 'James')]}]
['sister', 'son', 'grandfather']