Our culture has an unwritten rule for family gatherings: Don’t talk about religion or politics. But we as Christians know that staying silent about the gospel is the most unloving thing we could possibly do. The question becomes, then, how do we go about sharing the gospel with our unbelieving family members without starting World War 3?
Cover the Situation with Prayer
Sharing the gospel with family is often difficult because they have seen you at your best, but they have also seen you at your worst. They may not understand the fact that Christianity is not about people claiming to be perfect in and of themselves, and they may think that you are hypocritical. They don’t yet see their need for Jesus, and they may think that you only want to judge them.
The first step to sharing the gospel effectively with unbelieving family members is to pray. When a person comes to Christ, they do so in response to the work God has already done in their hearts. For this reason, you should be praying for God to soften their hearts to receive the gospel. You should also be praying for wisdom for yourself to have the words to say, to communicate the truth effectively, and to respond to them with grace.
Prioritize Building Up Your Relationship
Your family may know that you are a Christian, but they may not know that you care about them. If the only time you ever talk to them is at Thanksgiving or Christmas, they may never be inclined to listen to what you have to say. It is important for you to invest in their lives. Affirm the areas of their life that are God-honoring, and support them in their passions as they use the gifts God has given them.
Ask them about their beliefs, and show them that you really do care. Be the hands and feet of Jesus when they need help. Show them with your actions that you are striving to be more like Christ every day. Show them that you are a different person than you were before coming to know Jesus. 
Share About Your Own Struggles and Testimony
As you go about building up your relationship with them, look for opportunities to share gospel truths in the conversations you have. Ask yourself if you have ever shared your testimony with them. If you haven’t, ask them if it would be okay for you to do so. Invite them to coffee or sit with them in the stands at their kid’s baseball game and have an honest conversation with them. 
Talk to them about how your life was before coming to know Jesus, how you came to know Jesus, and how your life is different after coming to know Jesus. Tell them about how you came to realize you were a sinner who couldn’t save yourself and how Jesus paid the debt you couldn’t pay. Explain to them that it was the best decision you ever made and that you would love for them to know what it is like to have Jesus change their life, too.
Model Repentance and Forgiveness
Then, live out the gospel you have shared with them. When you sin against them, go to them, admit that what you did was wrong, and ask for forgiveness. Demonstrate humility and repentance. Make every effort not to sin against them in the same way again. You won’t be perfect. Acknowledge that and use it to point them to Jesus.
And when they sin against you, choose to forgive them. Have a grace-filled conversation with them, and let them know that what they did hurt you. Then, initiate forgiveness. Don’t expect them as an unbeliever to act like a believer. Rather, give them a tangible example of what it looks like to humble yourself and admit wrongdoing. And give them a tangible example of what it looks like for God to remember their sins no more.
Appeal to the Bible as Your Source of Authority
Look for gospel bridges in your conversations with the members of your family who are unbelievers. Let them know that you do not believe what you believe simply because you woke up one day and decided to hold a controversial position about sin. And you don’t believe what you do because you hate them or have any ill feelings towards them. Show them that what you believe comes from the Bible.
Try not to communicate truth in an “it’s true because I believe it to be so” kind of way. Rather, appeal to the Bible as your source of authority. Try saying instead something like “the Bible reveals itself as the Word of God, and I believe that to be true. I want to submit to the authority of God as He has outlined it. The Bible says (fill in the blank) about this situation.” Then, if they are willing, show them where in Scripture it says what you are saying. 
But always remember to give an answer for the hope that you have with gentleness and respect (1 Peter 3:15). Be diligent about making sure that you do not think of yourself as higher or better than them. D. T. Niles once described sharing the gospel with helpful imagery: You are just one beggar giving another beggar directions about how to get to the Bread of life.
Be Willing to Invest in Them for the Long-Haul
Sharing the gospel with unbelieving family members is not a one-time event. If you truly want them to come to the knowledge of the truth, you must be willing to exercise patience. It will take a while to establish credibility with them, especially if you haven’t been acting out your faith around them very well. But don’t give up! Keep exposing them to truth in a loving way. Keep showing them that you care. Keep praying for them. And above all, entrust their soul to the Lord. He loves people far more than we ever could.