I think what the OP is asking is, what are the consequences for a JW who knowingly permits, as houseguests, an unmarried couple (not JW) to stay overnight in their (the JW’s) home.
There’s a whole section on this in the elders manual, chapter 12 (particularly 12:66-69). That publication is available on dozens of websites so I won’t post links here. But here is the outline:
— If the elders find out about it, they’re supposed to “counsel” the JWs who are allowing apparent “fornication” in their home
— Hopefully, the JWs respond and kick out the fornicating couple
— If the JWs “brazenly” defy the elders and allow the formicating couple to remain as houseguests, they (the JWs) would be subject to a “marking talk” and lose any “privileges of service” they may have
— If the JWs go a step farther and “promote immortality” by talking about their situation to others in the congregation, they could be subject to a judicial committee for “causing divisions”
— A (grudging) exception is made for special cases, such as elderly JW parents allowing a non-JW son/ daughter + unmarried partner to stay in the home. But even in that case, the elderly JW parents would be subject to “review” of any “privileges of service”.
Hope that helps.