What about items of other family members?
In a perfect life situation, each family member should have a separate place to store personal stuff, their own space. Even if it is not a separate closet, at least separate shelves in a common closet. The main point is that your things should not be stored in one place.
If we are talking about an adult, then their separate space should be their area of responsibility. You can put things in order in the closet or room of your husband, wife or grown up child only after you get their permission. It will be wonderful if you and your close family agree to follow the program together.
Instilling respect for order in children is as important as instilling all other values. Only a personal example and a “do as I do” approach will work, there is nothing worse than notations and phrases like “clean up your room, or you won’t go for a walk!”.
Firstly, adults must become adherents of order, then children will become interested in it too. It is important that this happens naturally and without coercion. You can help this process if you immediately start involving them in the upkeep of order and showing them exactly how to do it.