qumquat The entire Spanish speaking world manages with double barrelled names, why does the 'what will happen when they get married, 4 names?!?!?' crop up everything this is discussed?
It did indeed become a problem in Germany. When the equality of men and women was written into the German constitution in 1957, for the first time married women received the right to keep their own name (even if it was only as the second name in a double surname)
From 1978, women had the right to have their own surname in first place in a double-barrelled name. And they did. It was, after all, a victory for feminist campaigners. A partial one - if parents disagreed about the surname for their children, the husband automatically won (women didn't really hold high positions at work, so the lawmakers said, and could be expected to change their name). That law was only changed in 1991 - if the parents disagreed, the court tossed a coin (not joking) or the kids could have both surnames.
Anyway, German women were so enthusiastic about this, that within a few years there were double-barrelled kid's surnames everywhere. So then the discussion started about double-barrelled lovebirds marrying and combining their name to triple or even quadruple-barrelled surnames.
There are constantly court cases where women are still trying to do this. But they all lose, because the German law has an incredibly low tolerance for this kind of chaos (imagining a few generations down the line eight or even ten surnames).
So they changed the law again in 1994. No more double-barrelled names allowed (unless you already have one, but even then you cannot add another name to that - double names is the maximum).
From then on, parents had to pick a new name or one of their existing surnames as a family name - this is the surname the children get. Either spouse can choose to change or keep their own name, adopt the new family name or add their own surname to the family name (unless that's the existing double-barrelled surname of one of the spouses).
So if Mr Black marries Ms White, they can choose Black or White as the surname for their future kids, and the partner whose name hasn't been chosen as the family name, can add their own surname to the family name as Mrs or Mr Black-White or Mrs White-Black but the partner with the family name cannot add the spouses name. And if Mr Black-White marries Ms Grey, they can only pick Black-White or Grey as their surname - Black-White-Grey is totally illegal.
We really are so lucky that the UK is totally fine with double surnames...