> Children seem to benefit primarily from watching relationships that genuinely make both parents happy.

I think you'll find the data supports chidren benefiting from a happy loving home. Not from the concern of the parents relationships with others.

My childhood friends were mostly from divorced parents and it very much impacted them all in negative ways. Parents are security blankets for children. It's who they run to when scared and need love. They are dependent on them survival. Ripping that apart causes harm.

It's not all just about the relationship, but about the father and mother. Both offer very different aspects of life that help children develop in a way they'd never get from something like a 'visiting' parent, let alone the Big Brothers/Sisters program. Those latter things are of course much better than nothing, but the ideal is an ever present father and mother. For but one example, the most obvious is that a father understands what a 13 year old boy is going through in a way a mother never could, yet that mother will do a far better job with that same boy in his early years than the father ever could.

Statistically children from two parent households just do dramatically better by just about every single measurable metric, with 0 control for the quality of that household/relationship.

My friend in high school suffered from depression in part because he was well aware of that fact that his parents were only staying together until he graduated. Despite any attempt to put a rational face on it, he believed his existence was the source of his parents' unhappiness.

Another friend of mine is doing this with his wife right now. He's utterly miserable, but the racial stereotype of the missing black father weighs so heavily in his mind that he's resigned to just counting down the years (despite my own attempt to convey the above story).