We live in a townhouse with 3 floors and have 3 bathrooms. Me and my wife have an ensuite in our bedroom, we have have a family bathroom the two boys have a bathroom on the top floor (where their bedrooms are. The bathroom has his and hers sinks and a shower.
Whenever the boys use the bath or shower they never clean the bath or shower after themselves. Me, my wife and dd are tied of having to clean the bath or shower before we use them.
So I have said that if the boys are happy to wash in a dirty bath and shower then they can both share their bathroom. They also never clean the his and hers sinks and one of the sinks is covered in charcoal cleanser, the cupboard is full of used deodorant cans and other products that the boys can't be bothered to throw away.
So aibu to do this until they start cleaning up after each other.