[Constance] asked her sister [Martha] if she could come over for dinner. [Martha] told her she could n't, because she had to care for her sick son, [Robert].
('Constance', 'Robert')
[Constance] asked her sister [Martha] if she could come over for dinner. [Martha] told her she could n't, because she had to care for her sick son, [Robert].
[{('Constance', 'nephew', 'Robert'): [('Constance', 'sister', 'Martha'), ('Martha', 'son', 'Robert')]}]