[Rich] and her sister [Alma] decided to take a trip to Mexico together. [Rich] and his sister [Helen] were twins. Still, they did n't look very much alike. [Katherine] took her sister [Helen] out for dinner to celebrate her birthday.
('Alma', 'Katherine')
[Rich] and her sister [Alma] decided to take a trip to Mexico together. [Rich] and his sister [Helen] were twins. Still, they did n't look very much alike. [Katherine] took her sister [Helen] out for dinner to celebrate her birthday.
[{('Alma', 'sister', 'Katherine'): [('Alma', 'sister', 'Helen'), ('Helen', 'sister', 'Katherine')]}, {('Alma', 'sister', 'Helen'): [('Alma', 'brother', 'Rich'), ('Rich', 'sister', 'Helen')]}]