In order to sin, know something is sinful, and you have to intend to offend God by doing it. If this is something that is nagging at you, then you should ask your parish priest for direction, the best place would be in the confessional.
Gay and Lesbian people are like ourselves sinners. Having a sexual desire is not sinful, it is how we act on it that can be. Unmarried people have no rights to the sexual act, from a moral point of view, heterosexual or homosexual. While this is a hard moral precept for some people to practice, we should all strive to uphold it. Oftentimes people want to point out someone elses sins, (it does not seem to be your primary intention here.) forgetting their own sinfulness. What you did not ask but I’ll put in my two cents is that the two men either come to a closer relationship with God, including a chaste life, and that you can be an example of chatity.
Chatity does not mean no sexual relationships, it simply means that if someone is married they are faithful to their mate, and if unmarried they remain celbate until they are married. Hopefully by cooperating with God’s graces we can all be examples of the kind of lives God wants us all to live, according to our state of life.