[Glen] was having a cookout one day, and invited his sister [Emily]. [Emily]'s brother [Milton] drove them to the cookout.
('Milton', 'Glen')
[Glen] was having a cookout one day, and invited his sister [Emily]. [Emily]'s brother [Milton] drove them to the cookout.
[{('Milton', 'brother', 'Glen'): [('Milton', 'sister', 'Emily'), ('Emily', 'brother', 'Glen')]}]
['sister', 'brother']