One piece of evidence which I can't believe you don't take seriously is the huge percentage of births to unwed mothers. Around one third of all births in the US are to unwed mothers, in the black community it's 75+% percent. Think about those numbers. In the UK it's 49%.
Social implosion due to the destruction of the family. Kids raised in what used to be called "broken homes" become very damaged, generally speaking. Of course, some overcome the damage. But many, many don't. Kids raised without their own mother and father in the home are at an extreme disadvantage, much higher incidences of drug/acohol use, molestation, violent behavior, acting out, promiscuity, and they have a much worse track record at being able to form stable marriages themselves.
If this doesn't herald danger to you, then you are either shutting your eyes willingly, or have extremely odd standards.
The definitions of "family" are shifting because of societal pressures. In a few years, the nuclear family, which many believe to be the norm, will become more and more rare. It may prove to be an economically unsustainable model for a lot of people. More than likely a large portion of nuclear families will be replaced by the multi-generational extended families.
The extended family is actually a more efficient use of resources in regards to child care and other expenses etc.
And yes, unwed mothers are a problem. But again, this has to do with economics. It's a phenom that thrives when people have very limited time horizons. And time horizons tend to be influenced by economics.