A key is a small object carrying an enormous amount of meaning. Handing one to a parent or parent-in-law is often done in a warm moment — after a house move, before a holiday, when a baby arrives — and almost never revisited afterwards. Then, months or years later, someone lets themselves in while you are still in a dressing gown, or reorganises your kitchen cupboards as a favour, and you discover that a decision made in five minutes has been quietly shaping your home life ever since.
The stories that circulate about in-laws overstepping tend to be dramatic. The everyday version is smaller and far more common: a person you love, who means well, who treats your front door as an extension of their own.
Separate the key from the permission
Most conflicts here are not really about the key. They are about the assumption that comes with it. A key is practical — someone can water the plants, let the plumber in, collect a parcel, help in an emergency. Permission is about when a person may use it. Those two things get bundled together, and the bundling is what causes the trouble.
So make them separate out loud. "You keep the key for emergencies and for when we ask, and otherwise we'll always be expecting you." That single sentence, said calmly and early, prevents years of resentment. If you would rather not have a spare in circulation at all, a small key safe by the door, with a code you can change whenever you like, gives you all the practicality and none of the ambiguity.
