It actually is, as sustainable marriages are the most fertile.

There are different methods for achieving "kids" or even "more kids", but the most reliable path is to just find one woman and treat her well-enough to stick around. That's why men have evolved to treat women well. 

 Sustainable happy marriages have become quite uncommon. All of that is a wishful thinking. 
But sustainable happy marriages can be a measure of quality. I bet you are doing quite well on that.