PeterJohn,
These are difficult things to deal with and I am nto the best person to give advice here…For I have had some considerable “Logs” in my eyes over the years as well.
The first thing I would say to you is that nothing you say will be effective if they are not ready to hear it. So begin by being a good listener. Talking with them about what is happening in their lives etc and offering good, sound, loving, Christian advice and (name removed by moderator)ut on whatever matter is under discussion. This builds trust and makes sure that they do not see you as judgmental.
Second - Pray (of course) that the Holy Spirit enlighten you to know what to say when various issues come up. Again, this will lead you to offer good advice and (name removed by moderator)ut without seeming judgmental.
Third - be patient. If and when touchy subjects come up, whether in general or more specific, do not be afraid to speak clearly, but in charity, in support of the teachings of the Church. But be sure that they understand that you uphold their right of conscience to act as they see best. Again - this is a matter of keeping lines of communication open.
Then - as these things help you and them to grow closer you will gain greater insights into why they have chosen the paths they have. You will be able to offer them insights, reading material and other things that will help them to more fully and correctly form their conscience.
Remember though that you cannot “push” them. You can only “draw” them toward a more perfect union with God. This is why Jesus tells us to look to our own “Log” first.
I sincerely hope this is, in some small way, helpful.
Peace
James