[Nicholas] called his son [Milton] to tell him he saw [Mary], [Milton]'s wife, at the market today.
('Mary', 'Nicholas')
[Nicholas] called his son [Milton] to tell him he saw [Mary], [Milton]'s wife, at the market today.
[{('Mary', 'father-in-law', 'Nicholas'): [('Mary', 'husband', 'Milton'), ('Milton', 'father', 'Nicholas')]}]
['husband', 'father']