I used to belong to (another religion), and most of my family still does. I have tried to teach them the truth but it usually ends up just making them mad. Or they just think I’ve turned into a “religious fanatic”. Can one be saved and still pray to someone other than God and Jesus? I don’t see how, as that seems to be idolatry. They also still believe in works, not just grace. What is your advice on how best to convert them?
You can’t teach someone unless they want to learn. Our job is to confront, it’s the Holy Spirit who converts. Jesus said if they don’t receive your message shake the dust off your sandals and move on (Mark 6:11). In other words drop the subject.
The more you make them mad the less likely they are to ever listen. Witness by example and pray without ceasing instead. You’ll find it eases the tension and gives them time to think.