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. Marriage is holy, while homosexual acts go against the natural moral law. Homosexual acts “close the sexual act to the gift of life. They do not proceed from a genuine affective and sexual complementarity. Under no circumstances can they be approved”.
Sacred Scripture condemns homosexual acts “as a serious depravity... (cf. Rom 1:24-27; 1 Cor 6:10; 1 Tim 1:10). This judgment of Scripture does not of course permit us to conclude that all those who suffer from this anomaly are personally responsible for it, but it does attest to the fact that homosexual acts are intrinsically disordered”.(5) This same moral judgment is found in many Christian writers of the first centuries and is unanimously accepted by Catholic Tradition.
Those who would move from tolerance to the legitimization of specific rights for cohabiting homosexual persons need to be reminded that the approval or legalization of evil is something far different from the toleration of evil.
CONGREGATION FOR THE DOCTRINE OF THE FAITH: Considerations regarding proposals to give legal recognition to unions between homosexual persons
With the pretext of regulating one context of social and juridical cohabitation, attempts are made to justify the institutional recognition of de facto unions. In this way, de facto unions would turn into an institution, and their rights and duties would be sanctioned by law to the detriment of the family based on marriage. The de facto unions would be put on a juridical level similar to marriage; moreover, this kind of cohabitation would be publicly qualified as a “good” by elevating it to a condition similar to, or equivalent to marriage, to the detriment of truth and justice. In this way, a very strong contribution would be made toward the breakdown of the natural institution of marriage which is absolutely vital, basic and necessary for the whole social body...
If the family based on marriage and de facto unions are neither similar nor equivalent in their duties, functions and services in society, then they cannot be similar or equivalent in their juridical status...
Marriage and the family are of public interest; they are the fundamental nucleus of society and the State and should be recognized and protected as such. Two or more persons may decide to live together, with or without a sexual dimension but this cohabitation is not for that reason of public interest. The public authorities can not get involved in this private choice. De facto unions are the result of private behavior and should remain on the private level.Pontifical Council for the Family: Family, marriage and "de facto" unions.