More Awesome Than You!

I don't know if this is a bug or glitch but suddenly all the new immigrants into my neighborhood have the same last names as my custom sims. They are not common names, not particularly uncommon either, Finnegan, Taylor, Brown and Lyons. Every new family has one of those names, it's quite annoying. To avoid confusion (mine) I have to rename them. Anyone else having this problem? Is there anything that can be done about it?  ???