[Pat]'s mother, [Guadalupe], waited impatiently for him at the diner. [Milton] rushed to the hospital to find out that his wife and already given birth to a boy and had named him [Pat]. [Arlene]'s husband, [Christopher], and sister, [Margaretta], came over for Easter brunch. [Milton], [Margaretta]'s father, came early and brought a bottle of apple cider from the market.
('Christopher', 'Guadalupe')
This example is mother-in-law.