We should go back to using profession as last name. Then everybody would be named Shitposter.

Spain. This is how you make Spain.

I believe this is a thing in Quebec.

from https://culturalatlas.sbs.com.au/canadian-culture/canadian-culture-naming

In Quebec, the Civil Code requires parents to assign their child only one surname (either a single or compound surname) derived from their respective surnames. Compound surnames may not have more than two parts, with or without hyphens. Thus, a couple named Joseph BOUCHARD-TREMBLAY and Marie DION-ROY could give their children the surnames:

• BOUCHARD
• TREMBLAY
• DION
• ROY
• BOUCHARD-TREMBLAY
• DION-ROY
• BOUCHARD-DION
• BOUCHARD-ROY, and so on.

In Quebec, the law provides that spouses retain their respective birth names when they are married.

In the Hispanic tradition it would be the Paternal name and then the Maternal name using the Paternal line, which would be the first name.

So Male 1-2 and Female 3-4 becomes Baby 1-3.

They keep going like a memory game.

In Canada, they typically pick one or two last names out of four for the kid. Some adults decide to go by just one of their last names too

I'm Brazilian and here in Brazil there's no well defined culture on what to do with family names. Legally, you can come out with a complete new family name at the moment of marriage, with the only rule that both people should have it.

In my case, my parents already had some long names. Dad 1 2 3 and Mom 4 5. Both me, my sister and my mom end up with 4 5 2 3, I believe because pressure from my grandparents.

By the way, having four family names, like I do, is not very common in Brazil. It is more common to have two, both the last names from the parents, e.g. Dad 1 2 and Mom 3 4 would result in Baby 4 2, with one of the parents optionally taking those names too (traditionally the woman).

as always – it depends on the jurisdiction.
But in most cases, they will use a new hyphenated last name that consists of both partners' first last name, with the man's first last name first.

Believe it or not, sexism!

They usually place the man's name first and then only pass on those names.

We just made up portmanteau names for our kids, based on what sounded good. Over time, this should improve the overall coolness of last names.

The names should be combined to make a new last name as your making a new family

You talk about it and decide together.

In our case we both kept our last names. Why change her last name when that’s who she’s always been? Really simplifies things as far as paperwork goes. Also - LPT: when you have different last names you can get double the introductory offers on things like internet packages at home. Just sign up under one name, cancel when able, sign up under the other. They don’t know you’re married.

I always assumed they would recall the frustrations of growing up with a hyphenated name and not pass that on to another child.

I read an article about this a few years ago, and the answer is whatever they want. I remember one couple said they just decided they liked the wife's grandmother's maiden name, so they just picked that. She was confused but flattered.

I've always thought the system of last names should be hyphenated. Your paternal last name first, maternal last name second. Women no longer change their names when marrying. Men pass the paternal name down to their kids, women pass down the maternal. That way last names are essentially a record of who your OG matrons and patrons are.

Latino person here with two last names.

I chose to keep both of mine, but when I married I only kept the first.

We also commonly only use the first in spite of having both in our ID

pretty sure the world ends.