I wasn't going to comment on this one, but changed my mind...
Bev, - you and your DH raised your son with with a certain set of values, no? As a Christian, to compromise those values would not be helping your son IMHO.
Even if he *is* living a celibate life in Chicago with his significant other, he really shouldn't be putting you through the worry of wondering what he and she are up to in your family home. Wouldn't you be all the time wondering if you put your son's wants before GOD'S Commandments?
I know what you are going through, because I've been there, and in fact am STILL there.
We have two daughters (both in their mid-twenties) who have been living with their respective "significant others" for several years now. We have *never* permitted them to sleep in the same bedroom in our home, and never will unless and until they are married.
This came up recently actually, and our eldest daughter was complaining that her SO "wouldn't commit," and she really wants to marry him and have children before she gets too much older.
So, I put on my "mommy" hat, sat her down and told her that *nobody* bothers to buy a cow when they are getting the milk for free! I didn't really think that would change anything, since she's been living with her SO for a couple of years now, in his parent's (otherwise Christian) house.
However, a couple of days after our talk, my daughter called home and told me/us that she had moved into her own bedroom in his parents house (they offered), and is now paying $300 a month in rent plus paying for her own food etc. No more sleeping together, until they are married, period.
Her SO has since told her he'd be "honored to have her as his wife," and they plan to get married in about six months. I don't see a ring yet, so I'm still in a "wait and see" mode on that one, but at LEAST our daughter is moving in the right direction. (Thank You LORD!)
My point in telling you this, is to say that by sticking to your guns (beliefs) and *not* compromising, you may just be helping your son *and* his SO more than you think.
Every situation is unique of course, and I don't presume to tell you what you should do with your own son. I *do* feel strongly that it's important *never* to put family before GOD though Bev. There are family members I have lost because of my stance as a Christian, - most of my relatives in fact. It isn't easy, but then Jesus told us this could happen, didn't He...
May GOD grant you the courage and the peace to do what you understand to be the right thing to do, - no matter *what* it costs you.
I say this with all the love in my heart Bev. May GOD be with you all.
Dee.