My twins' rooms are certified disaster areas. Sometimes you can barely identify the carpet color because there are so many clothes strewn about. Stacks of books and piles of papers cover every flat surface. Despite differences in other aspects of their personalities, they are definitely alike in their disarray.
However, things were much worse when they shared a room. Now, at least they are responsible for their own mess, and they do clean up every so often. (If by "clean up," you mean shuffle the mess around.) Back when they shared a space, clean-up was an endless battle as they fought over whose mess it was and who was responsible for managing it. Having their own room does give twins a sense of accountability for their personal space and for taking care of their belongings. That was one of the reasons we made the decision to move them into separate bedrooms.
Someday I hope that they will develop a "neat streak" and learn to live without clutter. For the time being, I've surrendered to the mess, rather than allow it to be a source of stress and contention. If you have any suggestions on how to manage the mess, please leave a comment and share your strategies!
What about your family? Do your twins share a room?