What you are describing sounds a lot like the Hunka relationship in Lakota culture. You might translate it as “relative by choice”, but it’s not meant to be in place of marriage (it’s usually between two men), nor do the two people live together. You can read about it here. It’s really more about two people who think of their relationship as being more like family than friends. At any rate, I think that’s as close as you’re going to get to their being a word for what you are looking for.
Well, they didn’t *need *porn - in any big city there was porn going on right in the taverns, streets and doorways. All you had to do was find the local “Gropecunt Lane” or similar.
And the married couple thing went both ways - if a couple didn’t look like they were doing much in the bedroom and People Started to Talk, or they went too long without having children, or the husband seemed like he was henpecked, or any of the two went dogging around while the marriage stalled ; the happy couple was stripped naked and paraded through the streets of the village ; or the whole village would gather and bang pots and pans in front of their house all day, that kind of thing. Public shaming used to be a big ticket item back in the day. Public everything, really. Even the biggest cities had that small town feel (which is a quaint way of saying everybody was all up in your shit all of the time), and your name & reputation was everything.
The GDR’s fertility policies actually worked quite well. I was surprised to learn this, since one tends to associate atheistic communist regimes with low fertility, but the GDR’s fertility rate in the early 1980s was around 1.9, compared to 1.3 or so in the west. (It drpped to much below the west in the 1990s, and today has converged around the same as the west).
There also continue to be plenty of countries which offer financial or other incentives for childbearing today. Overpopulation is a problem in some parts of the world but not others, over half the world’s countries have sub-replacement fertility, and so there are a lot of countries with fertility rates (and future population projections) lower than they would like.
This reminded me of another example from my own life.
My mother-in-law had a pair of spinster friends, who lived together for several decades; their partnership ended when one of the pair died a few years ago.
When I first met the two of them (when I started dating the woman I eventually married), I just assumed that they were a middle-aged lesbian couple. They were obviously very close, they co-owned a house, they traveled together, and they had been together for a long time. It wasn’t until some time later, after I got to know them, and finally asked my then-girlfriend about them, that I discovered that the two of them were not, in fact, romantically involved nor lesbians (and that they would have been deeply shocked and offended had I actually suggested such to them, as they were both highly conservative and traditional).
The surviving one of the couple is, I’m fairly certain, asexual – AFAIK, she’s never ever been involved in any sort of romantic or sexual relationship with anyone. She’s also always been extremely involved with the church, and, had she been raised Catholic instead of Lutheran, I have no doubt that she would have been a nun. The other one, I think, did have a relationship or two when she was younger, but she never married, and never dated while she was living with her friend.
ISTR that the two of them had filed “durable power of attorney” with each other, but there was, otherwise, obviously, no legal or cultural term for the relationship that they shared. And, I do know that, when the one was dying, she was having to make very certain that it was her friend (and not her family) who had the ultimate power to determine the course of her treatment and follow her wishes (something that would simply have been assumed if they were spouses).