[John] and [Katherine] have a daughter named [Tracy], and [Katherine] has a son named [Bret].
('Bret', 'John')
[John] and [Katherine] have a daughter named [Tracy], and [Katherine] has a son named [Bret].
[{('Bret', 'father', 'John'): [('Bret', 'sister', 'Tracy'), ('Tracy', 'father', 'John')]}, {('Bret', 'sister', 'Tracy'): [('Bret', 'mother', 'Katherine'), ('Katherine', 'daughter', 'Tracy')]}]