I have seen things that make me suspect my uncle is gay. He is also very feminine. I have seen on his phone him searching gay porn and in gay chat rooms. I know if my grandmother found out she would be devastated ... unless she already knows. The reason I'm telling you this is because my uncle is a Christian and is a member of the church of Christ. He comes to church every Sunday. My minister even has taught about homosexuality many. What should I do?
Looking at pornography, homosexual or heterosexual, is sinful (I Thessalonians 4:3-5). You know that your uncle is sinning, so it would be your responsibility to talk to him and try to persuade him to leave his sin behind. However, in order for this to be effective, you first have to look at your own life and make sure that you are not involved in similar sins. "For in the way you judge, you will be judged; and by your standard of measure, it will be measured to you. Why do you look at the speck that is in your brother's eye, but do not notice the log that is in your own eye? Or how can you say to your brother, 'Let me take the speck out of your eye,' and behold, the log is in your own eye? You hypocrite, first take the log out of your own eye, and then you will see clearly to take the speck out of your brother's eye" (Matthew 7:2-5). Therefore, before you can talk to your uncle, you need to be sure that you are not involved in pornography or looking lustfully at others.
Start out by asking why he is doing things that he knows is wrong. Then be prepared to listen and to hear things that you are very likely not going to like knowing. If you are unable persuade him, then collect evidence, so that it is not just your word against your uncle's word. Remember that it is by two or three witnesses that truth is established (Deuteronomy 19:15). Only then ask one or two men to come with you to talk to your uncle and see if you can talk him out of his sin. If that too fails, then it will be up to the church to decide what to do about his refusal to repent (Matthew 18:15-17).