Franze,
Well, the first answer is (as always) to pray for them without ceasing. And if God has laid a burden on your heart (if I may use the Baptist terminology I learned many years ago) for these people, that shouldn’t be very difficult.
One thing NOT to do is to compromise Church teachings. There is a world of difference between saying “your sins are forgiven” and saying “you have not sinned.” If the Church teaches that something is a sin, then it’s a sin and we shouldn’t pretend that it isn’t. We don’t need to obsess on it, but if and when the subject comes up it will need to be addressed.
I think that if a person is divorced and (illicitly) re-married, then the proper lifestyle for that person is celibacy within that marriage. (If I’m wrong, somebody please correct me.) I can appreciate that this can be a very hard thing to sell in today’s society.
If the person can’t handle it and goes off to another church, well, I’m sorry, but there probably isn’t a lot to do about it. Jesus let the rich young man walk away, after all.
I’m afraid I’ve not been very helpful.