I already am married (with children), and am quite happy in a monogamous relationship, as is my wife. However, we both know (and know of) several "couples" of three people. They seem happy and the children seem happy. It occurs to my wife and I that perhaps it is possible to love more than one person. Why not?
I also disagree with your comment that a male and female parent are the best option. I know two young children who are being raised by a lesbian couple. They are doing a great job, better than many male/female couples I know.
Why are three parents automatically bad, if everybody loves each other?
I thought it was an interesting thing to ponder. Don't you?
You want an example of where marriage has falledn apart and has contributed to a break down of morality? Then I would point you to many of our inner cities, where nearly 3/4 of children are born outside of wedlock. Where many males have numerous multiple partners. Now you can argue this point till your blue in the face, but the lack of fathers in many of these communities has contributed to crime, sex, drugs, and gangs. Most of these young kids are being raised by women. You need both a man and woman to properly raise a child.
It is better to encourage marriage, then to discourage it.
Is marraige perfect? By no means!! Are there a few outlyers who will defy the odds? Of course! But overall marraige is a good thing for society. Two parents are ideal. I'm sure some lesbians make great parents. But the number of homosexuals who want to have families I doubt is very large.