My sister, who is a lesbian, invited me to her wedding. I have been the “black sheep” of the family because I am a Christian. We want to show grace and love but we also stand firm in not attending. We don’t know how to decline in a way they won’t hate us and exclude us from the family. How do we decline lovingly?
I would say something like the following:
It breaks my heart to have to say no to coming, because with everything in me I want you to be happy. But I believe that happiness does not come outside of God's will, but only inside it. Therefore to celebrate something that is fundamentally wrong, according to God’s Word, would be to celebrate your hurt and ruin, and what will ultimately rob you of happiness, not bring it. (It would be like celebrating someone taking poison just because they want to; it may require more time to see it, but one day you will realize this for what it really is, and you will no longer believe it was right or good.)
It’s not a matter of me judging you. It's a matter of me submitting to what God has said. If I did not, I would be a hypocrite. Because hypocrites say they believe the Bible and trust God and recognize Him as the authority, not themselves, then turn around and fail to live and choose as if that is really true.
It would be easier for me to come and pretend all is well. But that would be untrue to my Jesus, who loves you and me just as we are, but loves us too much to let us stay that way. That’s why He died for us. And I love you enough to die for you. And I love you too much to pretend what you are doing is right and life-giving, when it is wrong and death-bringing. I cannot be a false witness. I dare not treat myself as God by turning my back on what He says, and I dare not treat you as God by doing what pleases you instead of doing what pleases God.
I will pray for God’s work in your life. He loves you and so do I.
(Keep in mind that you can say all this and she can still utterly reject you, of course. And your family can too. But I believe God would be pleased. And that is ultimately all that matters.)