Devin answered...

One of the core teachings of the Church is the eternal nature of the family relationship and that marriage and gender play foundational roles in that relationship. Gender is an immutable aspect of our identity that has been part of us from the beginning, before this life. Viewed from this eternal perspective, marriage is more than a contractual arraignment between two people. In the Gospel of Jesus Christ, marriage involves eternal commitments, including having children and teaching them to distinguish right from wrong. In addition to the ability to conceive children, Men and women have unique parental characteristics that, when combined, create the best scenario for raising those children. Those abilities and characteristics are not present in same-sex marriages.

As far as same-gender attraction goes, the Church's attitude mirrors that of its attitude to any sexual activity outside of the marriage relationship -- complete abstinence. In that sense, the Church does not distinguish between homosexuals and heterosexuals in how it looks upon sexual activity outside of marriage. It emphasizes the cultivation of heterosexual relationships at appropriate times because it is that relationship that leads to marriage.