Ryan - You said that "If your goal is healthy, happy children in a stable marriage, don’t have premarital sex."  This seems like a really slanted view.  It disregards the fact that (abstaining from) premarital sex isn't a strong indicator of marital success and/or happiness  It ignores the fact that my sex life shouldn't be affecting my children.

As for the research on cohabitation I mentioned, the only added divorce risk that children bring is for women bringing children into a second marriage.

I am a child of divorced parents.  Of course, my mother brought a child into her second marriage (with my father), so maybe they were doomed.  In the end, what affected them was their relationship and not being able to manage their conflicts.  I'm not going to sit here and blame it on premarital sex or whatever, because that's ultimately short-sighted.  They didn't belong together, and we're all better off that they separated.  On the other hand, just because someone got divorced doesn't mean they're no longer a good parent.  I know many divorced people who still have frequent positive contact with their former spouses and their kids benefit from what amounts to an even larger family.

Yes, it is beneficial for children to grow up in a loving, caring household.  That can be easier with two parents.  Sometimes... often perhaps, this isn't always in a traditional, happy heterosexual marriage.  Single parents can love and care for and provide for their children very well, and a married man and woman can yell at each other every night.  Two men or women can love each other and be in a committed relationship and take care of a number of kids better than some couples who have decided to wait until they're 30 to get married and have sex.  There's no one magic solution to creating a good marriage and happy, healthy kids.  Stop putting people in boxes and realize that there are plenty of people out there who are in happy, successful situations that may not fit into your narrow view of right and wrong.