[Ashley]'s grandson [Robert] was playing in the pool with his sister [Heidi].
('Ashley', 'Heidi')
[Ashley]'s grandson [Robert] was playing in the pool with his sister [Heidi].
[{('Ashley', 'granddaughter', 'Heidi'): [('Ashley', 'grandson', 'Robert'), ('Robert', 'sister', 'Heidi')]}]
['grandson', 'sister']