Maybe you could share this evidence instead of sharing an anonymous assertion

Sure. I'll also show you how, so you could do this yourself in future.

I googled "stability of cohabiting couples". This led me to Wikipedia [1]. From there I hit the 2002 CDC report "Cohabitation, Marriage, Divorce, and Remarriage in the United States" [2]. That provides the following statistic:

"The probability of a first marriage ending in separation or divorce within 5 years is 20 percent, but the probability of a premarital cohabitation breaking up within 5 years is 49 percent. After 10 years, the probability of a first marriage ending is 33 percent, compared with 62 percent for cohabitations."

I wondered if that had changed since 2002, so I hit Google Scholar and searched for articles after 2010. A 2020 article discussed cohabitation broadly. I scrolled down and found a 2018 article [3]. (There's an ungated PDF elsewhere if you need it.) They look at 8 countries including the US. Their findings: "cohabiting couples who do not subsequently transition to marriage... consistently have the highest predicted probabilities of separation within 5 years." Some of the gaps between cohabiting and married couples disappear if you control for (e.g.) education and other demographics.

[1] https://en.wikipedia.org/wiki/Cohabitation#Likelihood_of_spl... [2] https://www.cdc.gov/nchs/pressroom/02news/div_mar_cohab.htm [3] https://read.dukeupress.edu/demography/article/55/4/1389/167...

It's puzzling to me that you are getting downvoted instead of responses when it seems like your comment follows the whole progressive comment Hacker News thing... Or whatever it is they are going for this week.

i can certainly think of cases where the children and one parent are really much better off without the second

I had an unstable family and a lot of patchwork in my youth. Won't recommend it. It doesn't have to be negative, but it often comes with compromises. And children aren't stupid, they can leverage the conflict of their parents, but it isn't necessarily for their best in the long run.

I heavily dislike the illusionary idealism from some for something that can be quite a lot of work. The state of marriage is pretty much not relevant though. At least in my opinion.

Yes it happens, but isn't the rule. On average, it's ideal to have two happy, loving parents. But only on average!

Thinking in terms of averages and correlations should not justify absurd oversimplifications.

The average human being has 1.99 eyes.

It seems you might be missing the larger point and getting hung up in pedantry. Try taking a deep breath and a step back to consider the bigger picture.

They basically said stable relationships are more stable than unstable relationships and you want evidence?

Stable relationships are possible without marriage. Some people view these as synonyms and others see that as a clear mistake.

Oh sorry I read their comment incorrectly

Why are the only options "married couple" or "unmarried couple"? Or even "married couple" or "single parent"?

Why can't broader family structures be considered, and be stable?

Those are the options that have significant data.

No one knows how other models work. However, note that "stable" comes from the data. Maybe other models are stable, maybe they're not. Without data, it's simply unknown.