[Thomas] was at lunch with his father, [Ernest]. [Ernest]'s mother, [Mary], showed up an hour after they were set to meet.
('Mary', 'Thomas')
[Thomas] was at lunch with his father, [Ernest]. [Ernest]'s mother, [Mary], showed up an hour after they were set to meet.
[{('Mary', 'grandson', 'Thomas'): [('Mary', 'son', 'Ernest'), ('Ernest', 'son', 'Thomas')]}]