While it's not explicitly stated that Mr. and Mrs. Twit are *married*, they live together and their relationship is incredibly dysfunctional and unpleasant. They are constantly bickering, playing cruel tricks on each other, and generally make each other's lives miserable.
Here are some key points that make them an unpleasant couple:
* Cruelty to each other: They constantly pull pranks and engage in mean-spirited behavior.
* Disgusting hygiene: Both are incredibly messy and have a disregard for cleanliness.
* Lack of respect: They treat each other with disdain and show no signs of love or affection.
* Selfishness: They prioritize their own amusement over anything else, even the well-being of their pets.
While the book is ultimately about the Twits being outsmarted by the monkeys, their miserable relationship serves as a central theme and a source of humor for the story.