Behavior with a Family Member Who Has Not Returned to Faith

Hello, honorable Rabbi, I would like to consult. I have returned to faith, but all other members of my household are not religious. One of my sons (23 years old) has a girlfriend who has been coming to sleep at our place with him in the same room for some time, and they have been together for two years. Over time, this has started to bother me due to the prohibition before marriage. I accept that they sleep together elsewhere, but it bothers me that it happens under my roof. I tried talking to him, which caused arguments between us and also between me and my wife, and it has soured the atmosphere at home. I would like to hear your opinion on this matter. Does the fact that they sleep in my house affect or diminish the blessing in the house? Or is it also a sin for me when I allow them to sleep in my house? And if so, is there a prohibition on them sleeping in separate rooms? For example, when hosting on Shabbat, since his girlfriend observes Shabbat. Thank you very much in advance.

Hello and blessings 

The prohibition of being with a girlfriend before marriage does not occur because of you; even if you prevent them from coming, they will live together elsewhere. Therefore, when you allow them to live in your house, you are not complicit in their transgressions. 

From what it seems, the correct approach at the moment is to maintain good relations with them, and in this way, your positive influence on them will be much greater. 

Especially when the girlfriend observes Shabbat in your home, it can positively influence the son and the rest of the family if the relations between you are pleasant. 

It is clear that if you can influence them to live in separate rooms, you will save them from several prohibitions, and that is excellent. But if they are not willing to listen pleasantly, you do not need to argue with them about it. 

When a person does what God wants, he has a blessing.  

May God help everyone return to complete faith.