This is inspired from Luke's Two lists of favorite words.
My aunt Sally keeps this list of her favorite words tacked on the refrigerator:
My uncle Joe has this list of his favorites:
Which one of them would like the word Listen?
Both my aunt and uncle had this word on their list:
My aunt is British and my uncle is American.
My aunt and uncle wanted to seem up with the times:
My aunt added "lol"
My uncle added "brb"
Don't look at the forest, but the trees.
The two lists are mutually exclusive.
I excluded the English tag very much on purpose
Note: No computer science knowledge is necessary to solve this, but thinking like one is helpful.