[Charles] went to his grandmother [Frances]'s house for the summer. He had a wonderful time there. [Charles] went skiing with his brother [Chris]. [Chris]'s sister [Martha] watched from the ski lodge.
('Martha', 'Frances')
[Charles] went skiing with his brother [Chris]. [Chris]'s sister [Martha] watched from the ski lodge. [Charles] went to his grandmother [Frances]'s house for the summer. He had a wonderful time there.
[{('Martha', 'grandmother', 'Frances'): [('Martha', 'brother', 'Chris'), ('Chris', 'grandmother', 'Frances')]}, {('Chris', 'grandmother', 'Frances'): [('Chris', 'brother', 'Charles'), ('Charles', 'grandmother', 'Frances')]}]
['brother', 'brother', 'grandmother']