It is quite debatable if children actually stabilize marriages (I know a lot of counterexamples).

I would argue exactly the other way around: A lasting marriage is not itself the goal (though certainly nice to grow old together), but serves the purpose of raising offspring - that's what counts for every species that has survived.

I agree children can cause problems in relationships. My point was more that they're a very strong reason against splitting up.

“ I think what's helping ensure commitment in that case are the children, rather than the marriage. ”

This is the luxury belief. It feels true, it doesn’t conflict with secular values, but all the research points to it being false…