Homosexual Relations
Let's be clear up front: it is not in any way wrong to be homosexual. Homosexuality is hardwired into the brain and cannot be helped. We do not know the cause of homosexuality, or if there is a single cause. We must be compassionate and understanding of homosexuals. "They must be accepted with respect, compassion, and sensitivity." (CCC 2358)
This does not mean homosexuals have a free pass to perform illicit and vulgar acts in the name of "love". Sex outside of marriage, and sex without the goal of procreation, is wrong in any form. Period. End of discussion. As the Catechism of the Catholic Church says, "Homosexual acts are intrinsically disordered" (CCC 2357) and "Homosexual persons are called to chastity" (CCC 2359).
From Amoris Laetitia (an oft-misconstrued Apostolic Exhortation from Pope Francis): "As for proposals to place unions between homosexual persons on the same level as marriage, there are absolutely no grounds for considering homosexual unions to be in any way similar or even remotely analogous to God’s plan for marriage and family." You can read the full document from the Vatican website by clicking here [PDF].