[John]'s brother [Jerry] and mother [Lillian] met him early in the morning before his college graduation.
('Jerry', 'Lillian')
[John]'s brother [Jerry] and mother [Lillian] met him early in the morning before his college graduation.
[{('Jerry', 'mother', 'Lillian'): [('Jerry', 'brother', 'John'), ('John', 'mother', 'Lillian')]}]
['brother', 'mother']