[John]'s mother [Lillian] wanted to surprise him for his birthday, so she baked him a cake. [Lillian] took her son [Douglas] to school this morning because he missed the bus.
('John', 'Douglas')
[John]'s mother [Lillian] wanted to surprise him for his birthday, so she baked him a cake. [Lillian] took her son [Douglas] to school this morning because he missed the bus.
[{('John', 'brother', 'Douglas'): [('John', 'mother', 'Lillian'), ('Lillian', 'son', 'Douglas')]}]
['mother', 'son']