[Jerry]'s mother [Lillian] made a cake for his birthday and her other son [Douglas] ate a piece of it.
('Jerry', 'Douglas')
[Jerry]'s mother [Lillian] made a cake for his birthday and her other son [Douglas] ate a piece of it.
[{('Jerry', 'brother', 'Douglas'): [('Jerry', 'mother', 'Lillian'), ('Lillian', 'son', 'Douglas')]}]
['mother', 'son']