[Martha], [Pamela], and [Chris] planned a big surprise party for their mother, [Lena]'s fiftieth birthday.
('Chris', 'Martha')
[Martha], [Pamela], and [Chris] planned a big surprise party for their mother, [Lena]'s fiftieth birthday.
[{('Chris', 'sister', 'Martha'): [('Chris', 'sister', 'Pamela'), ('Pamela', 'sister', 'Martha')]}, {('Pamela', 'sister', 'Martha'): [('Pamela', 'mother', 'Lena'), ('Lena', 'daughter', 'Martha')]}]
['sister', 'mother', 'daughter']