Hey - for years we have made the stand that un married folks stay in separate rooms in our house.
I assume this might be considered extreme and 'forcing morality' on others.
Your thoughts ???
My father would not even welcome family (niece) to reunions and family gatherings if she brought her live-in boyfriend. —Not because he or anyone else was better than they, but because he considered having them there a public statement of acceptance of that lifestyle. Whether he would have done so if they were, for example, passing by, or visiting, I don't really know, though I think his niece would have known better than to ask.
For myself, I am more lax, though I agree with his 'public statement' POV. I have lesbian friends, 'married', who know where I stand on the matter. But then, they have no reason to impose. So, it's up to you. In the long run, what matters is its effect on them, I think. —Would they consider them staying in the same room in your house an acceptance of what they do?
Not to lay more on you than I like laid on me, but, "Whatsoever is not of faith is sin" may apply here. Make your mind up, and if you are wrong, at least let them know why you decided what you did.