Recently I've noticed many new sims in town having the last name of my characters, many also have hyphenated last names. For instance, in one world I have Holly Would (an obvious name), in another there is Valeri VaVoom (from a 1960s comic book ...yes, I'm that old, lol), in Sunlit Tides there is now a sim with last name Would-VaVoom. None of my sims have had offspring. Occasionally these names can be rather humorous - down the street in Sunlit Tides is the Pleasant-Dong family.

But how do I stop this?

This is normal behavior for immigration under EA or Nraas story progression. With Nraas, though, you can change it to behave differently. Also, there are quite a few names lists floating around that you can import to encourage the game to name your new sims the way you'd like. You can get several of them here or at the Nraas site.

Thanks; I tracked down several of those lists, will try the most recent.

I'm not too picky about what names are used, I just don't want my character names bandied about so much. And the plethora of hyphenated names is ridiculous (I'm old as dirt and have only known three people with such names in RL); will probably have to use MC and change many of those ...though maybe not the Pleasant-Dong family, that's just too funny.

What NRAAS settings can prevent this in the future?

I'm guessing immigration is pulling from your bin families.

You can set them as random for immigration, so they will be quite different. That's what I do.

I bolded the one for immigrant names.

City Hall/Computer > NRAAS > Story Progression > General Options

Options: Lots > Options: Immigration/Emigration >
Immigration Gauge = Default:0
Chance of Bin Offspring = Default:50
Chance of Random Offspring = Default:10
Chance of Teen Immigrant = Default:0
Immigrant Name = Father (Default:Mother-Father)
Random Sim Weight Range = Default:-1.0 : 1.0
Skin Tone Range = Default: 0 : 1
Whole Family Immigration Size = Default:8
Options: Lots > Options: Inspection > Prompt On Inspection Fail = True

Thanks, I'll give that a shot.