@Saddy-chin At the very least, the family should still be in the bin from when you originally created them in CAS. You would have had to place them from the library into town, so unless you deleted them, they'll still be there. (If you tried a clean folder, they'll be an entry in Library inside your old game folder.)
Even if they're not, you can bring up the cheat console (crtl-shift-c) and enter "testingcheatsenabled true" without quotes. Then shift-click on one sim and select "Edit in Create-a-Sim." Once in there, you should be able to save the sim to the bin (along the bottom of the screen, I think you want the ". . ." button). So when you're ready to start a new game, you can bring up the list of premade sims, and your sims will be there for you to put back together as a family. Sims saved this way are stored in files in your SavedSims folder.
Edit: Maybe the problem is that you already have a family of the same name (i.e. these sims when you created them) in your library. You can move those files out of your game folder (in Library) to see if it makes a difference.