[Dale] 'son [Travis] and [Travis]'s grandfather [Clarence] went on a cruise together.
('Dale', 'Clarence')
[Dale] 'son [Travis] and [Travis]'s grandfather [Clarence] went on a cruise together.
[{('Dale', 'father', 'Clarence'): [('Dale', 'son', 'Travis'), ('Travis', 'grandfather', 'Clarence')]}]
['son', 'grandfather']