Jesus christ. You need to sit them down and talk to them. THIS IS NOT APPROPRIATE. I had to tell my own mother it was not okay to just walk into our house. I asked her to please call before or at least ring the bell. Even if it is family they need to know the boundaries and what is socially acceptable. Tell them that from now on, they need to ring the bell or give you a call if they want to come over as you might be naked or have important clients over or some other reason why you might not want to be bothered. If it persists get a big dog that that is trained to hate strangers.